title: Dropzonejs - rename file before upload
body: <p>I have dropzone set-up and working with my AWS S3 account. However I want to be able to rename the file before it is sent to S3 (append with timestamp for example) so that a file uploaded with the same name as an existing file will not get overwritten. I've tried to catch this at the sending event and to update the file name at this point but without success:</p>
  
  <pre><code>this.on("sending", function(file) {
    file.name = 'my-new-prefix-' + file.name;
  });
  </code></pre>
  
  <p>Any ideas where I am going wrong or why this isn't working?</p>
  
  <p>Also have raised this earlier at - <a href="https://github.com/enyo/dropzone/issues/345" rel="nofollow">https://github.com/enyo/dropzone/issues/345</a></p>