$routeChangeSuccess documentation

I hope this helps someone, I ran into some issues when following the API as described - handlers of this event receive 3 arguments, not 2.

Although this is mentioned [elsewhere](http://docs.angularjs.org/api/ng.$rootScope.Scope#$on) it's not clear when viewing the docs for this behaviour in isolation. 

The first argument is an Event Object, not the current route. The previous route argument can also be omitted on occasions.