Fix required modules due to changes in ActionView and rendering in Rails 4.1

* Due to changes in Rails 4.1.0.beta1 with the abstraction of action_view and
the rendering changes, we have to explicitly require/include these extra things
so that AbstractController::Rendering is included early enough.
* AbstractController::Rendering has a dependency on action_view.
* ActionView::Rendering is required for the :status option of render.
Extract test for response status and make sure we can override the default.