fixes browserify task transforms support

grunt/tasks/browserify.js

@@ -46,7 +46,7 @@ module.exports = function() {
   };
 
   // TODO: make sure this works, test with this too
-  config.transforms.forEach(bundle.transform, this);
+  config.transforms.forEach(bundle.transform, bundle);
 
   // Actually bundle it up
   var _this = this;