Changed default parent class of InheritedResources::Base.

I always had this issue with namespaced applications, but that could be easily overcome by defining an pointer constant to the namespaced ApplicationController.

Now I have a namespaced Rails Application, that depends on an namespaced Rails Engine, that uses active_admin, which uses inherited_resources. And none, including the application itself have an ApplicationController in the root.

Also I would raise the discussion about moving Base to the lib directory, and have maybe an InheritedResources::ApplicationController < ::ApplicationController; inherit_resources; end 
if one needs it.

I don't really understand your architecture of tests, otherwise I would have written one for this change.
For backwards compatibility I would suggest an generator or something that creates an initializer. 

Greetings.