Fix namespaced anonymous controller routes

Fixes #952.

I'm not fully happy still with how this is implemented. I spent a bit of time digging around the resources and how they get created. While this does give us the equivalent of using a proper `namespace` route, we may not need all the complex `:as`, `:module`, and `:path` options.

In general, my opinion is that people should not be using anonymous controllers and expecting to be able to use a named route for them; nor should they be relying on the URI path they are mapped to.

Finally, the specs for this are still incomplete. It's was a bit difficult to figure out a clean way to verify that the routes were properly configured. They are defined only in a `before` action currently. This requires either some heavy mocking, which I fully believe is the wrong approach, or setting up an example run - which I couldn't get to work. I'll submit a separate PR for some brainstorming on these changes.