Allow border between th cells and td cells when used inside a panel

Created by: kenperkins

As of 3.1, when you do:

<div class="panel panel-default">
  <table class="table table-bordered">
    <thead>
      <th>foo</th>
    </thead>
    <tbody>
      <tr>
        <td>baz</td>
      </tr>
    </tbody>
  </table>
</div>

You get no border between the head and the body like in 3.0.x. It comes back if you remove table-bordered but then you don't have vertical separators between columns.

Without table-bordered: