title: jsTree dnd events not firing
body: <p>I'm trying to capture dnd events in jsTree 3.0.0. I used the demo code to build event handlers.  The tree builds fine, but the events never fire. What am I missing?</p>
  
  <p>This is the pertinent part. The JSON works fine and builds the tree itself find.  However, the console.log calls never occur when I drag and drop on the tree.</p>
  
  <pre><code>&lt;link href="/jquery/jquery-ui-1.10.3/css/ui-lightness/jquery-ui-1.10.3.custom.min.css" rel="Stylesheet"/&gt;
  &lt;script src="/jquery/jquery-ui-1.10.3/js/jquery-1.9.1.js"/&gt;
  &lt;script src="/jquery/jquery-ui-1.10.3/js/jquery-ui-1.10.3.custom.min.js"/&gt;
  &lt;link href="/jquery/plugins/jsTree/themes/default/style.min.css" rel="stylesheet"/&gt;
  &lt;script src="/jquery/plugins/jsTree/jstree.js"/&gt;
  &lt;script&gt;
      $(function () {
          $('#jstree')
          // listen for events
          .on('dnd_start.vakata', function (e, data) {
              console.log('Dragged');
          })
          .on('dnd_stop.vakata', function (e, data) {
              console.log('Dropped');
          })
          // create the instance
          .jstree({
              "core" : {
                  "check_callback" : true,
                  'data' : {                              
                      'url' : 'categoriesJson.pm?json=1',
                      'data' : function(node) {
                          console.log (node);
                          return {
                              'id' : node.id
                          }
                      }
                  },
                  "themes" : {
                      "stripes" : true
                  }
              },
              "plugins" : [ "dnd" ]
          });
  
          $(document).bind("drag_stop.vakata", function (e, data) {
              if (data.data.jstree) {
                  console.log('User stopped dragging');
              }
          });                 
      });
  &lt;/script&gt;                   
  </code></pre>