title: Missing extension when save image on paperclip
body: <pre><code> image = PortfolioFileItem.find(107)  
   img_source = "http://s3.amazonaws.com/test/portfolio_file_items_final/original/1.jpg"
   image.picture_from_url(img_source)
   image.save(false)
  </code></pre>
  
  <p>image save DONE but missing extensionof image. this is sample image name saved:
   open-uri20110528-6779-fpiust-0.</p>
  
  <p>Please help me solved problem. thanks</p>