Throttling args

Laravel 5.2 already has throttling though I prefer the Dingo API's throttling due to some additional features. However, the new middleware groups would be benefit from having the throttling defined directly in the middleware string ala `api.throttle:30,1` instead of passing additional values, so that the middleware group array can leverage it as here https://github.com/laravel/laravel/blob/master/app/Http/Kernel.php#L35