**Contents**

* TOC
{:toc}

<a class="btn btn-primary" role="button" data-toggle="collapse" href="#contents" aria-expanded="false" aria-controls="contents">Contents</a>

<div id="contents" class="collapse" markdown="1">

* TOC
{:toc}

</div>
Make spec table of contents collapsible.
Make spec table of contents collapsible.

Spec's TOC is very long. This adds a button to toggle collapse-reveal
of TOC. Initially collapsed.
