module ActiveAdmin
  class Engine < Rails::Engine
    if Rails.version > "3.1"
      initializer "ActiveAdmin precompile hook" do |app|
        app.config.assets.precompile += %w(active_admin.js active_admin.css active_admin/print.css)
      end
    end
  end
end

module ActiveAdmin
  class Engine < Rails::Engine
    if Rails.version > "3.1"
      initializer "ActiveAdmin precompile hook", :group => :all do |app|
        app.config.assets.precompile += %w(active_admin.js active_admin.css active_admin/print.css)
      end
    end
  end
end

Make sure assets are precompiled on Heroku
Make sure assets are precompiled on Heroku

Heroku recommends that `config.assets.initialize_on_precompile = false`,
which means that this initializer will not be invoked by
`rake assets:precompile`, which forces developers deploying to Heroku
to duplicate this initializer in their apps' configs.
