allow extraFields to be a function

Author: gunjanpatidar

jquery.html5_upload.js

@@ -156,6 +156,7 @@
                     if (window.FormData) {//Many thanks to scottt.tw
                         var f = new FormData();
                         f.append(typeof(options.fieldName) == "function" ? options.fieldName() : options.fieldName, file);
+                        options.extraFields = typeof(options.extraFields) == "function" ? options.extraFields() : options.extraFields;
                         $.each(options.extraFields, function(key, val){
                             f.append(key, val);
                         });