I tried putting sass-rails before rails suggested in the post Bundler gem compatibility issues when deploying to heroku. but it didn't work.
Heroku Error Message
Bundler could not find compatible versions for gem "railties":
In Gemfile:
rails (= 4.0.0) ruby depends on
railties (= 4.0.0) ruby
sass-rails (= 4.0.0) ruby depends on
railties (4.0.1.rc1)
Failed to install gems via Bundler.
Gemfile
source 'https://rubygems.org'
ruby '2.0.0'
gem 'sass-rails', '4.0.0'
gem 'rails', '4.0.0'
gem 'pg', '0.15.1'
gem 'bcrypt-ruby', '3.0.1'
group :development, :test do
gem 'rspec-rails', '2.13.1'
end
group :test do
gem 'selenium-webdriver', '2.35.1'
gem 'capybara', '2.1.0'
gem 'factory_girl_rails', '4.2.1'
end
gem 'uglifier', '2.1.1'
gem 'coffee-rails', '4.0.0'
gem 'jquery-rails', '3.0.4'
gem 'turbolinks', '1.1.1'
gem 'jbuilder', '1.0.2'
group :doc do
gem 'sdoc', '0.3.20', require: false
end
group :production do
gem 'rails_12factor', '0.0.2'
end