EDIT: The general advice is to use CEDAR stack.

Pretty new to RoR, Gems, Heroku and Git. Following tutorial: http://ruby.railstutorial.org/book/ruby-on-rails-tutorial

Works smoothly on localhost, when deployed to Heroku got ConnectionNotEstablished error, that was solved here:
https://stackoverflow.com/questions/7542745/heroku-error-activerecordconnectionnotestablished (BTW: following same tutorial) After changing production database to PostgreSQL (gem 'pg') it generates another error:

Visting live site

An error occurred in the application and your page could not be
served. Please try again in a few moments.

If you are the application owner, check your logs for details.

Tried this –
Heroku app crashed, receiving "Invalid DATABASE URL" when attempting heroku rake db:migrate –
heroku rake db:migrate

rake aborted!
Invalid DATABASE_URL

Tasks: TOP => db:migrate => db:load_config
(See full trace by running task with --trace)

heroku console

Internal server error

gemfile

source 'http://rubygems.org'

gem 'rails', '3.1.1'

group :development do
  gem 'rspec-rails', '2.6.1'
  gem 'annotate', '~> 2.4.1.beta' 
  gem 'sqlite3'
end

group :test do
  gem 'rspec-rails', '2.6.1'
  gem 'webrat', '0.7.1'
  gem 'sqlite3'
end

group :production do
    gem 'pg'
end

group :assets do
  gem 'sass-rails',   '~> 3.1.4'
  gem 'coffee-rails', '~> 3.1.1'
  gem 'uglifier', '>= 1.0.3'
end

heroku logs

9:02+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/lib/thin/runner.rb:143:in `run!'
9:02+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/bin/thin:6:in `<top (required)>'
9:02+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/lib/thin/runner.rb:177:in `run_command'
9:02+00:00 app[web.1]:   from /home/heroku_rack/heroku.ru:18:in `block (2 levels) in <main>'
9:02+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/rack-1.3.6/lib/rack/builder.rb:51:in `initialize'
9:02+00:00 app[web.1]:   from /usr/ruby1.9.2/bin/thin:19:in `<main>'
9:02+00:00 app[web.1]:   from /usr/ruby1.9.2/bin/thin:19:in `load'
9:03+00:00 heroku[web.1]: State changed from starting to crashed
9:04+00:00 heroku[web.1]: Process exited
1:58+00:00 heroku[slugc]: Slug compilation started
3:09+00:00 heroku[api]: Deploy 3dea426 by mstefanow@gmail.com
3:09+00:00 heroku[api]: Release v7 created by mstefanow@gmail.com
3:09+00:00 heroku[web.1]: State changed from crashed to created
3:09+00:00 heroku[web.1]: State changed from created to starting
3:10+00:00 heroku[slugc]: Slug compilation finished
3:12+00:00 heroku[web.1]: Starting process with command `thin -p 44881 -e production -R /home/heroku_rack/heroku.ru start`
3:15+00:00 app[web.1]: (erb):9:in `rescue in <main>': Invalid DATABASE_URL (RuntimeError)
3:15+00:00 app[web.1]:   from (erb):6:in `<main>'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/1.9.1/erb.rb:753:in `eval'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/1.9.1/erb.rb:753:in `result'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/application/configuration.rb:106:in `database_configuration'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/lazy_load_hooks.rb:36:in `instance_eval'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/railtie.rb:68:in `block (2 levels) in <class:Railtie>'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/lazy_load_hooks.rb:36:in `execute_hook'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/lazy_load_hooks.rb:43:in `block in run_load_hooks'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/lazy_load_hooks.rb:42:in `each'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/lazy_load_hooks.rb:42:in `run_load_hooks'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activerecord-3.1.1/lib/active_record/base.rb:2190:in `<top (required)>'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:240:in `require'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:240:in `block in require'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:225:in `load_dependency'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:240:in `require'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:489:in `load_missing_constant'
3:15+00:00 app[web.1]:   from /app/app/models/user.rb:12:in `<top (required)>'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:179:in `each'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:179:in `const_missing'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/inflector/methods.rb:124:in `block in constantize'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/inflector/methods.rb:123:in `each'
3:15+00:00 a
 from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/inflector/methods.rb:123:in `constantize'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/core_ext/string/inflections.rb:43:in `constantize'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:348:in `require_or_load'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:181:in `block in const_missing'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/actionpack-3.1.1/lib/action_controller/metal/params_wrapper.rb:148:in `_default_wrap_model'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/actionpack-3.1.1/lib/action_controller/metal/params_wrapper.rb:167:in `_set_wrapper_defaults'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/actionpack-3.1.1/lib/action_controller/metal/params_wrapper.rb:128:in `inherited'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/actionpack-3.1.1/lib/abstract_controller/railties/routes_helpers.rb:7:in `block (2 levels) in wi

3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/actionpack-3.1.1/lib/action_controller/railties/paths.rb:7:in `block (2 levels) in with'
3:15+00:00 app[web.1]:   from /app/app/controllers/users_controller.rb:1:in `<top (required)>'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:240:in `block in require'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:225:in `load_dependency'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:240:in `require'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:240:in `require'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:348:in `require_or_load'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:302:in `depend_on'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/activesupport-3.1.1/lib/active_support/dependencies.rb:214:in `require_dependency'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/engine.rb:417:in `block (2 levels) in eager_load!'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/engine.rb:416:in `each'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/engine.rb:416:in `block in eager_load!'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/engine.rb:414:in `each'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/engine.rb:414:in `eager_load!'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/application/finisher.rb:51:in `block in <module:Finisher>'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/initializable.rb:30:in `instance_exec'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/initializable.rb:30:in `run'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/initializable.rb:55:in `block in run_initializers'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/initializable.rb:54:in `each'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/initializable.rb:54:in `run_initializers'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/application.rb:96:in `initialize!'
3:15+00:00 app[web.1]:   from /app/config/environment.rb:5:in `<top (required)>'
3:15+00:00 app[web.1]:   from <internal:lib/rubygems/custom_require>:29:in `require'
3:15+00:00 app[web.1]:   from <internal:lib/rubygems/custom_require>:29:in `require'
3:15+00:00 app[web.1]:   from config.ru:3:in `block (3 levels) in <main>'
3:15+00:00 app[web.1]:   from /home/heroku_rack/heroku.ru:23:in `eval'
3:15+00:00 app[web.1]:   from /home/heroku_rack/heroku.ru:23:in `block (3 levels) in <main>'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/railties-3.1.1/lib/rails/railtie/configurable.rb:30:in `method_missing'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/rack-1.3.6/lib/rack/builder.rb:120:in `new'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/rack-1.3.6/lib/rack/builder.rb:120:in `map'
3:15+00:00 app[web.1]:   from /home/heroku_rack/heroku.ru:18:in `block (2 levels) in <main>'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/rack-1.3.6/lib/rack/builder.rb:51:in `instance_eval'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/rack-1.3.6/lib/rack/builder.rb:51:in `initialize'
3:15+00:00 app[web.1]:   from /home/heroku_rack/heroku.ru:11:in `new'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/rack-1.3.6/lib/rack/builder.rb:51:in `instance_eval'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/rack-1.3.6/lib/rack/builder.rb:51:in `initialize'
3:15+00:00 app[web.1]:   from /home/heroku_rack/heroku.ru:11:in `block in <main>'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/rack-1.3.6/lib/rack/builder.rb:51:in `instance_eval'
3:15+00:00 app[web.1]:   from /app/.bundle/gems/ruby/1.9.1/gems/rack-1.3.6/lib/rack/builder.rb:51:in `initialize'
3:15+00:00 app[web.1]:   from /home/heroku_rack/heroku.ru:1:in `new'
3:15+00:00 app[web.1]:   from /home/heroku_rack/heroku.ru:1:in `<main>'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/lib/rack/adapter/loader.rb:36:in `eval'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/lib/rack/adapter/loader.rb:36:in `load'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/lib/thin/controllers/controller.rb:175:in `load_rackup_config'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/lib/thin/controllers/controller.rb:65:in `start'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/lib/thin/runner.rb:143:in `run!'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/bin/thin:6:in `<top (required)>'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/bin/thin:19:in `load'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/bin/thin:19:in `<main>'
3:15+00:00 app[web.1]:   from /usr/ruby1.9.2/lib/ruby/gems/1.9.1/gems/thin-1.2.6/lib/thin/runner.rb:177:in `run_command'
3:16+00:00 heroku[web.1]: State changed from starting to crashed
3:17+00:00 heroku[web.1]: Process exited
5:55+00:00 heroku[router]: Error H10 (App crashed) -> GET high-wind-7473.heroku.com/pages/home dyno= queue= wait= service= status=503 bytes=
5:57+00:00 heroku[router]: Error H10 (App crashed) -> GET high-wind-7473.heroku.com/pages/home dyno= queue= wait= service= status=503 bytes=

Kind of stuck, please help (point in right direction)

Of course

bundle install
git add .
git commit -m "another heroku fix"
git push
git push heroku