title: jquery ui droppable but not some child elements
body: <p>I want to drag and drop but exclude some child elements from the drop zone with jQueryUI Droppable like:</p>
  
  <pre><code>&lt;div id="dropZone"&gt;
    &lt;div&gt;&lt;/div&gt;
    &lt;div&gt;&lt;/div&gt;
    &lt;div&gt;exclude this container&lt;/div&gt;
  &lt;/div&gt;
  </code></pre>