Port-an-existing-app-to-OOD.md

@@ -23,6 +23,11 @@ Do this through the dashboard web UI or via the shell on apps-test.awesim.org.
 +gem 'rails', '4.1.15'  # You may also use a newer version
 ```
 
+Follow the update guides for:
+
+* http://guides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-4-0-to-rails-4-1
+* http://guides.rubyonrails.org/upgrading_ruby_on_rails.html#upgrading-from-rails-4-1-to-rails-4-2
+
 ##### Update `sass-rails`
 
 ```diff