Rack::Attack is a class

We're fixing all places that reference ```Rack::Attack``` as a module. Also I had to add the ```.class``` in the instance of ```Rack::Attack``` that overrides ```throttled_response```.

[![LGTM](http://www.lgtm.in/p/aZUlMDrkn)](http://www.lgtm.in/i/aZUlMDrkn)