A Gemfile that I use for Rails 4 projects deployed on Heroku.

Rails Gemfile.rb

source 'https://rubygems.org'
ruby "2.0.0"

# Bundle edge Rails instead: gem 'rails', github: 'rails/rails'
gem 'rails', '4.0.1'

# Use sqlite3 as the database for Active Record
gem 'sqlite3'

# Use SCSS for stylesheets
gem 'sass-rails', '~> 4.0.0'
gem 'bourbon', '~> 3.1.8'

# Use Uglifier as compressor for JavaScript assets
gem 'uglifier', '>= 1.3.0'

# Use CoffeeScript for .js.coffee assets and views
gem 'coffee-rails', '~> 4.0.0'

# See https://github.com/sstephenson/execjs#readme for more supported runtimes
# gem 'therubyracer', platforms: :ruby

# Use jquery as the JavaScript library
gem 'jquery-rails'

# Turbolinks makes following links in your web application faster. Read more: https://github.com/rails/turbolinks
gem 'turbolinks'

# Build JSON APIs with ease. Read more: https://github.com/rails/jbuilder
gem 'jbuilder', '~> 1.2'

group :doc do
  # bundle exec rake doc:rails generates the API under doc/api.
  gem 'sdoc', require: false
end

# Use ActiveModel has_secure_password
# gem 'bcrypt-ruby', '~> 3.1.2'

# Use unicorn as the app server
gem 'unicorn'

# Use Capistrano for deployment
# gem 'capistrano', group: :development

group :development, :test do
  gem "guard", "~> 2.2.3"
  gem "guard-livereload", "~> 2.0.0", require: false
  gem 'sqlite3'
end

group :production do
  gem 'pg'
  gem 'rails_12factor'
  gem 'rails_serve_static_assets'
end