title: parsley js - conditional required if checkbox checked
body: <p>Is there an easy way with parsleyjs to make a field required depending on another field?</p>
  
  <p>See my js fiddle here <a href="http://jsfiddle.net/marksteggles/wbhLq0t4/1/" rel="noreferrer">http://jsfiddle.net/marksteggles/wbhLq0t4/1/</a></p>
  
  <pre><code>&lt;form data-parsley-validate="true"&gt;
      &lt;div class="form-group"&gt;
          &lt;label&gt;
              &lt;input name="request_signature" type="checkbox" /&gt;Require signature&lt;/label&gt;
          &lt;div class="request_signature_fields"&gt;
              &lt;textarea class="form-control required" name="signature_reason" rows="3"&gt;&lt;/textarea&gt;
          &lt;/div&gt;
      &lt;/div&gt;
      &lt;input class="btn btn-success" name="commit" type="submit" value="Send" /&gt;
  &lt;/form&gt;
  </code></pre>