appraise 'rails3.1' do
  gem 'rails', '~> 3.1.0'
end

appraise 'rails3.2' do
  gem 'rails', '~> 3.2.0'
end

appraise 'rails4.0' do
  gem 'rails', '~> 4.0.0'
  gem 'protected_attributes'
  gem 'rails-observers'
end