title: django-storage with s3-boto break browser cache
body: <p>I have a django project which use django-storage over s3-boto.</p>
  
  <p>Problem is that every file that is located on S3 unable to cache because the url is changed from each call.</p>
  
  <p>here are two calls generated by django-storage :</p>
  
  <pre><code>https://my.s3.amazonaws.com/cache/user_6/profile_pic/profile_profile_picture_thumbnail.jpg?Signature=HlVSayUIJj6dMyk%2F4KBtFlz0uJs%3D&amp;Expires=1364418058&amp;AWSAccessKeyId=[awsaccesskey]     
  https://my.s3.amazonaws.com/cache/user_6/profile_pic/profile_profile_picture_thumbnail.jpg?Signature=xh2VxKys0pkq7yHpbJmH000wkwg%3D&amp;Expires=1364418110&amp;AWSAccessKeyId=[awsaccesskey]
  </code></pre>
  
  <p>As you can see the signature is different. What can I do so it wont break my browser cache ?</p>