Allow OPTIONS request

lib/util.js

@@ -40,7 +40,7 @@ var util = {
   },
   allowCrossDomain: function(req, res, next) {
     res.setHeader('Access-Control-Allow-Origin', '*');
-    res.setHeader('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE');
+    res.setHeader('Access-Control-Allow-Methods', 'GET,PUT,POST,DELETE,OPTIONS');
     res.setHeader('Access-Control-Allow-Headers', 'Content-Type');
 
     next();