title: Tag-it onlyAvalaibleTags option doesn't work
body: <p>I use tag-it plugin from <a href="https://github.com/aehlke/tag-it/downloads" rel="nofollow">https://github.com/aehlke/tag-it/downloads</a>. How to  disable adding new tags?</p>
  
  <pre><code>$(document).ready(function () {
                  $("#Tags").tagit({
                      singleField: true,
                      singleFieldNode: $('#mySingleField'),
                       //  onlyAvailableTags : true,
                       allowNewTags: false,
                      tagSource: [@Html.Raw(ViewBag.AvailableTags)]
                  });
              });
  </code></pre>
  
  <p>I tried to use <code>onlyAvailableTags : true</code> and <code>allowNewTags: false</code> options, but there's no effect.</p>