Teach the railtie to detect engines in Rails 3
Teach the railtie to detect engines in Rails 3

In Rails 3.1 the Railties class has an `#engines` method that does what
we want. Regrettably, in Rails 4 onwards this seems to be removed and
instead `Rails.application.railties` includes `Enumerable` instead.

trailblazer/trailblazer-rails,trailblazer/trailblazer-rails