title: jsTree nodes don't expand/collapse
body: <p>Can't get jsTree nodes to expand collapse. I must be missing something very simple.</p>
  
  <p>This is the script </p>
  
  <pre><code>&lt;script type="text/javascript" src="&lt;%= Url.Content("~/Scripts/jquery.jstree.js") %&gt;"&gt;&lt;/script&gt;
  &lt;script type="text/javascript"&gt;
          $(document).ready(function () {
              Refresh();
          });
  
          function Refresh() {
              $('#technologyTree').jstree({
                  "json_data": {
                      "ajax": {
                          "url": "/TechnologyVersions/TechnologiesTreeAjax",
                          "type": "GET",
                          "dataType": "json"
                      }
                  },
  
                  "plugins": ["themes", "json_data", "ui"],
  
                  "themes": {
                      "theme": "default",
                      "dots": true,
                      "icons": true,
                      "url": " &lt;%= Url.Content("~/Content/jsTree/themes/default/style.css") %&gt; "
                  }
              });
          }
  &lt;/script&gt;
  </code></pre>
  
  <p>I can see the tree populated correctly and the json result from the controller seems correct. However when I click on those expand/collapse arrows nothing happens. </p>