Update knockout.mapping reference path

knockout/knockout-tests.ts

@@ -1,5 +1,5 @@
 /// <reference path="knockout-2.2.d.ts" />
-/// <reference path="knockoutmapping-2.0.d.ts" />
+/// <reference path="../knockout.mapping/knockout.mapping-2.0.d.ts" />
 
 declare var $;