title: CarrierWave how to store file at given url
body: <p>I have CarrierWave working fine through the typical ORM setup and upload via form. I would like to figure out how to use CarrierWave outside of the form submission context. For example, when a user registers I would like to grab their gravatar and store it with CarrierWave. Here's what I have, and it does not work:</p>
  
  <pre><code>gravatar_url = "http://www.gravatar.com/avatar/#{Digest::MD5.new.update(current_user.email)}?s=512&amp;d=identicon"
  
  uploader = ImageUploader.new
  uploader.store! gravatar_url
  </code></pre>
  
  <p>No error either. I've been looking around the web and have not been able to find a solution.</p>