bootstrap-sass compatibility in Rails 4.0

application.rb

# As of Rails 4.0 we need to add a line to config/application.rb to make bootstrap-sass compatible with the asset pipeline

require File.expand_path('../boot', __FILE__)
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module YourApp
  class Application < Rails::Application
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    .
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    config.assets.precompile += %w(*.png *.jpg *.jpeg *.gif) #Add this line
  end
end