ScrollSpy requires <element class="nav">

Created by: unruthless

ScrollSpy relies on your navigation markup being patterned like

<[element] class="nav">
  <ul>
    <li><a href="#link">Link</a></li>
    ...
  </ul>
</[element]>
</pre>

or

<ul class="nav">
  <li><a href="#link">Link</a></li>
</ul>

But the docs do not specify that the element wrapping the <li>'s must have class="nav".

Happy to submit a pull request -- would it be better to update the docs to make this required markup clear, or better to update the plugin to accept an arbitrary class and/or ID on the list wrapper?