chore(grunt): do not rewrite gif urls

Author: btford

lib/grunt/utils.js

@@ -303,7 +303,7 @@ module.exports = {
   rewrite: function(){
     return function(req, res, next){
       var REWRITE = /\/(guide|api|cookbook|misc|tutorial|error).*$/,
-          IGNORED = /(\.(css|js|png|jpg)$|partials\/.*\.html$)/,
+          IGNORED = /(\.(css|js|png|jpg|gif)$|partials\/.*\.html$)/,
           match;
 
       if (!IGNORED.test(req.url) && (match = req.url.match(REWRITE))) {