title: render_to_string in lib class not working
body: <p>I'm trying to use <code>delayed_job</code> to update a remote database via xml</p>
  
  <p>In my lib folder I put a file with a class that should do a <code>render_to_text</code> with <code>template.xml.builder</code>, but I get:</p>
  
  <pre class="lang-none prettyprint-override"><code>undefined method `render_to_string' for #&lt;SyncJob:0x7faf4e6c0480&gt;...
  </code></pre>
  
  <p><em>What am I doing wrong?</em></p>