Add a callout during login to allow end-users to attach things to the

login promise.

@@ -251,6 +251,10 @@ define(function(require) {
                 } else {
                     result = $.Deferred().resolve().promise();
                 }
+                var onLogin = self.get('onLogin');
+                if (onLogin) {
+                    result = onLogin(result);
+                }
                 return result;
             };
             this.logout = function() {