user registrations

this AddUser method will eventually work just like current_user does in rails. right now it lacks the functionality of pulling the current user from the session because we haven't set that up yet. So all it does is generate a new user from params passed in via form. 

That's one major difference I see between Revel and Rails so far. Where in rails we would handle the raw params in the controller body, it seems that Revel tries to assert a type on the params before they reach the controller.