title: jquery validate check at least one checkbox
body: <p>I have something like this:</p>
  
  <pre><code>&lt;form&gt;
  &lt;input name='roles' type='checkbox' value='1' /&gt;
  &lt;input name='roles' type='checkbox' value='2' /&gt;
  &lt;input name='roles' type='checkbox' value='3' /&gt;
  &lt;input name='roles' type='checkbox' value='4' /&gt;
  &lt;input name='roles' type='checkbox' value='5' /&gt;
  &lt;input type='submit' value='submit' /&gt;
  &lt;form&gt;
  </code></pre>
  
  <p>I would like to validate that at least one checkbox (roles) should be checked, is it possible with jquery.validate ?</p>