PR138#commitcomment-4293036 use full namespace when specifying a classtype

See https://github.com/juliandescottes/piskel/pull/138#commitcomment-4293036

js/utils/Serializer.js

@@ -33,7 +33,7 @@
     /**
      * Similar to deserializePiskel, but dealing directly with a parsed piskel
      * @param  {Object} piskelData JSON.parse of a serialized piskel
-     * @return {Piskel} a piskel
+     * @return {pskl.model.Piskel} a piskel
      */
     createPiskel : function (piskelData) {
       var piskel = null;
@@ -84,4 +84,4 @@
       return piskel;
     }
   };
-})();
+})();