title: Using the Rails Environment URL in a MODEL with paperclip
body: <p>in my users model I have a paperclip setup like this:</p>
  
  <pre><code>  has_attached_file :profile_pic, 
                      :styles =&gt; {:large =&gt; "300x300&gt;", :medium =&gt; "150x150&gt;", :small =&gt; "50x50#", :thumb =&gt; "30x30#" },
                      :default_style =&gt; :thumb,
                      :default_url =&gt; '/images/:attachment/default_:style.png',
  </code></pre>
  
  <p>How do I make the default URL, include the full URL? </p>
  
  <pre><code>http://0.0.0.0:3000/images/:attachment/default_:style.png 
  or http://sitename.com/images/:attachment/default_:style.png
  </code></pre>