Temporary patch for raising an exception

If the padrino project is including uninitialized constant, `NameError` should be raised.
But the error won't be raised because [the active_support's extension](http://api.rubyonrails.org/v2.3.8/classes/ActiveSupport/CoreExtensions/Module.html#M000806) and [Padrino::Routing#parent](https://github.com/padrino/padrino-framework/blob/master/padrino-core/lib/padrino-core/application/routing.rb#L244) are colliding.

This patch fixes the error by using temporary patch.
Also, I'd like to drop the active-support gem and implement similar extensions as parts of padrino-support. Thoughts?