reference json module rather than dojo global

todo-example/dojo/js/todo/store/LocalStorage.js

@@ -53,7 +53,7 @@ define(["dojo/_base/declare", "dojo/_base/lang", "dojo/_base/json", "dojo/store/
             //		property if a specific id is to be used.
             //	returns: Number
             var id = options && options.id || object[this.idProperty] || Math.random();
-            localStorage.setItem(id,dojo.toJson(object));
+            localStorage.setItem(id, json.toJson(object));
             return id;
         },
         add: function(object, options){