Fix collectables link

Author: greggman

index.html

@@ -111,7 +111,7 @@ <h2><a href="%(url)s">%(name)s</a></h2>
       by: "Greggman",
       desc: 'An unfinished demo inspired by <a href="http://www.geeks3d.com/20090615/pixel-city-procedurally-generated-city-in-opengl/">Pixel City</a>.',
     },
-    { url: 'collectibles/collectibles.html',
+    { url: 'collectibles/index.html',
       img: 'collectibles/collectibles.jpg',
       name: 'Collectibles',
       by: "Human Engines",