flatstack::rails_application depends on flatstack::rails

`recipe[rails_application]` depends on `recipe[rails]` because it uses attributes of the latter and notifies `service[nginx]` defined in the latter.

Actually I see little sense in keeping these 2 recipes separate as `recipe[rails]` is nearly empty. I'd better combine them into a single recipe. Please let me know if you think it is a good idea and I'll combine them.