fixed issue with backbone and added zepto

Signed-off-by: Tj Holowaychuk <tj@vision-media.ca>

assets.json

@@ -240,9 +240,15 @@
   },
   "backbone": {
     "url": "https://github.com/documentcloud/backbone/raw/{version}/backbone.js",
-    "compressed": "backbone-min.js"
+    "compressed": "backbone-min.js",
     "description": "Backbone supplies structure to Javascript Apps by providing models, views, collections, and events",
     "tags": ["js"],
     "version": "0.3.3"
+  },
+  "zepto": {
+    "url": "https://github.com/madrobby/zepto/raw/v{version}/src/zepto.js",
+    "description": "zepto.js is a minimalist inlinable framework for mobile WebKit browsers, with a jQuery-like chaining syntax",
+    "tags": ["js"],
+    "version": "0.5"
   }
 }