Added UMD approach to the module

backbone-model-file-upload.js

@@ -3,7 +3,15 @@
 //     For all details and documentation:
 //     https://github.com/homeslicesolutions/backbone-model-file-upload
 
-!function(_, Backbone){
+(function (root, factory) {
+    if (typeof define === 'function' && define.amd) {
+        // AMD. Register as an anonymous module.
+        define(['underscore', 'backbone'], factory);
+    } else {
+        // Browser globals
+        factory(_, Backbone);
+    }
+}(this, function(_, Backbone){
 
   // Clone the original Backbone.Model.prototype
   var backboneModelClone = _.clone( Backbone.Model.prototype );
@@ -114,4 +122,4 @@
 
   });
 
-}(_, Backbone);
+}));