title: droppable in droppable
body: <p>I have this markup</p>
  
  <pre><code>&lt;ul id="hello" class="cat"&gt;
      &lt;ul id="a1" class="cat"&gt;
      &lt;/ul&gt;
      &lt;ul id="a2" class="cat"&gt;
      &lt;/ul&gt;
  &lt;/ul&gt;
  </code></pre>
  
  <p>I did this thing</p>
  
  <pre><code>$("ul.cat").droppable(
  {
      drop:function()
      {
          alert($(this).attr("id"));
      }
  });
  </code></pre>
  
  <p>It always write "hello".
  only "hello".
  How can I bind droppable on childs too?</p>
  
  <p>UPD: I want drop in elements in #hello's chidlren AND #hello itself. I want to determine where li was dropped.</p>