 is the DOM element in which to create the timeline.
    </li>
    <li>
      <code>items</code> is an Array containing items. The properties of an
      item are described in section <a href="#Data_Format">Data Format, items</a>.
    </li><li>
    <code>groups</code> is an Array containing groups. The properties of a
    group are described in section <a href="#groups">Data Format, groups</a>.
  </li>
    <li>
      <code>options</code> is an optional Object containing a name-value map
      with options. 