Remove Lotus::Controller DSL

Closes #49 
@joneslee85 In full stack applications we use this namespace: `Bookshelf::Controllers`, it would be repetitive to have `Bookshelf::Controllers::ArticlesController::Show`, that's want to encourage this new naming.

In standalone mode, we should suggest developers to put their controllers under `Controllers` as well, to avoid name clashes. Eg. `Identity` (model domain object) and `Identity::Index` (controller + action).

Does it makes sense?