Add introspection in controllers as @app instance variable

I'd like to contribute to rumm, and my first thought was to create a more complete 'help' command. The best way I can think of to do this is to add introspective capabilities to mvcli so that we can check the routes in the controller, and via the routes describe what commands are available.

I'm making this pull request now so that you can review the changes and think about whether this makes sense for your project. I can add specs if you like the direction.