title: Asset_sync gem skipping PDF files
body: <p>I recently configured the asset_sync gem to sync all of my assets to Amazon S3.  I deploy on Heroku, and for whatever reason, it seems to be skipping all PDF files in my <code>/app/assets</code> directory.  I haven't told it to exclude any files, why might this happen?</p>
  
  <p>I've followed this guide: <a href="https://devcenter.heroku.com/articles/cdn-asset-host-rails31" rel="nofollow">https://devcenter.heroku.com/articles/cdn-asset-host-rails31</a>, and as such I don't have an <code>asset_sync.rb</code> initializer file.</p>
  
  <p>I've tried moving the PDFs to their own dir, <code>/app/assets/pdfs</code>, and no dice there either.</p>
  
  <p>Strangely, I have a .zip file in the <code>/app/assets/images</code> dir, so it seems like specifically PDFs are being skipped.</p>
  
  <p>Rails 3.2.13, Ruby 2.0, Heroku Cedar Stack, current release of <code>asset_sync</code> gem</p>