title: Delete files before uploading via Fineuploader
body: <p>(using fineuploader with Traditional endpoints)</p>
  
  <p>Application flow:</p>
  
  <ul>
  <li>User will upload several files</li>
  <li>Server will perform some backend operations on theses files</li>
  <li>Files will then be deleted</li>
  </ul>
  
  <p>Because of these "backend operations" it would be cleaner to delete all the files in the upload directory before any files are uploaded.  Fineuploader has a lot of callbacks.  My thinking was add a callback for <a href="http://docs.fineuploader.com/branch/master/api/events.html#validateBatch" rel="nofollow">validateBatch</a>.  Then I could kick off my delete operation, but how do I then indicate to fine uploader to continue.</p>