title: Paperclip does not allow jpg upload, even though it is sepcified in content type.
body: <p>I am using paperclip to accept image uploads. I have the following validation on my attachment:</p>
  
  <pre><code>validates_attachment :image, content_type: { content_type: ['image/jpg', 'image/png'] }, size: { in: 0..500.kilobytes }
  </code></pre>
  
  <p>Uploading a png works fine, but uploading a jpeg does not work, and results in a save error which is displayed in the form. The error is on image_content_type. How can I debug this problem? </p>