Adding scrollbar to bootstrap tokenfield autocomplete
<p>I couldn't find any documentation or questions about enabling scroll bar on bootstrap's tokenfield autocomplete.</p>

<p>My field has a lot of users form Active Directory and it's mandatory for us to have this scroll.</p>

<pre><code>  $(usersList).tokenfield({
    autocomplete: {
      source: values,
      delay: 10,
      focus: function (event, ui) {
        event.preventDefault();
        $(this).val(ui.item.label);
      }
    },
    showAutocompleteOnFocus: true
  });

  //prevent adding duplicate values
  $(usersList).on('tokenfield:createtoken', function (event) {
    var existingTokens = $(this).tokenfield('getTokens');
    $.each(existingTokens, function(index, token) {
      if (token.value === event.attrs.value)
      event.preventDefault();
    });
  });
</code></pre>