title: callback issue with carrierwave and mongoid
body: <p>I am using carrierwave and mongoid on a rails 3 application and am having an issue with an after_save callback.  Consider the following</p>
  
  <pre><code>class Video
    include Mongoid::Document
  
    field :name  
  
    mount_uploader :file, VideoUploader
  
    after_create :enqueue_for_encoding
  
    protected
  
    def enqueue_for_encoding
       // point your encoding service to where it expects the permanent file to reside
       // in my case on s3 
    end
  
  end
  </code></pre>
  
  <p>My issue is that in my <code>enqueue_for_encoding</code> method, file.url points to the local tmp directory not the s3 directory.</p>
  
  <p>How do I get my <code>enqueue_for_encoding</code> method to be called when file.url points to s3?</p>
  
  <p>Thanks!</p>
  
  <p>Jonathan</p>