Make getParentRouter() method optional when implementing new routers

Author: andreypopp

lib/environment/Environment.js

@@ -71,7 +71,7 @@ Environment.prototype.register = function register(router) {
     this.start();
   }
 
-  if (!router.getParentRouter()) {
+  if (router.getParentRouter === undefined || !router.getParentRouter()) {
     this.routers.push(router);
   }
 }