Filter all keys starting with underscore

src/Ratchet/Http/Router.php

@@ -49,7 +49,7 @@ class Router implements HttpServerInterface {
 
         $parameters = array();
         foreach($route as $key => $value) {
-            if (!in_array($key, array('_controller', '_route'))) {
+            if ((is_string($key)) && ('_' !== substr($key, 0, 1))) {
                 $parameters[$key] = $value;
             }
         }