Description:
    Create <model_name>.rb to app/models/ by using comment.rb template.
    Create create_<model_name>s.rb to db/migrate by using create_comments.rb template.

Example:
    rails generate commentable <model_name>

    This will create:
        app/models/<model_name>.rb
        db/migrate/<time_stamp>_create_<model_name>s.rb

