Fix parens in uuid4

This was causing event_ids to be generated as 33 chars long instead of
32

Author: mattrobenolt

src/utils.js

@@ -126,8 +126,8 @@ function uuid4() {
             return v;
         };
 
-        return pad(arr[0]) + pad(arr[1] + pad(arr[2]) + pad(arr[3]) + pad(arr[4]) +
-        pad(arr[5]) + pad(arr[6]) + pad(arr[7]));
+        return pad(arr[0]) + pad(arr[1]) + pad(arr[2]) + pad(arr[3]) + pad(arr[4]) +
+        pad(arr[5]) + pad(arr[6]) + pad(arr[7]);
     } else {
         // http://stackoverflow.com/questions/105034/how-to-create-a-guid-uuid-in-javascript/2117523#2117523
         return 'xxxxxxxxxxxx4xxxyxxxxxxxxxxxxxxx'.replace(/[xy]/g, function(c) {