use returned uploder obj

Author: SunLn

example/js/main.js

@@ -1,4 +1,4 @@
-Qiniu.uploader({
+var uploader = Qiniu.uploader({
     runtimes: 'html5,flash,html4',
     browse_button: 'pickfiles',
     container: 'container',
@@ -48,6 +48,10 @@ Qiniu.uploader({
     }
 });
 
+uploader.bind('FileUploaded', function() {
+    console.log('hello man,a file is uploaded');
+});
+
 $(function() {
     $('#container').on(
         'dragenter',