Hook responseAlter

I've created a hook called ```responseAlter``` that allows for a last change on the payload being answered to a request. It is proving to be very useful on my project. This hook receives the *payload* object (which will by default have at least ```status.code``` data), the *request* object, and the *response* object. Only the *payload* object should be modified, as modifying the *request* or the *response* should cause for no changes because this is really a last call and all processes have already taken place. They serve only as informative objects.