Single buttons do not follow markup position

[awidener3]

Buttons that are within a <dd> seem to pop out of the flow similarly to this issue for checkboxes/radios: #253

It can probably be solved in the same way.

<dl>
  <div>
    <dt>...</dt>
    <dd>...</dd>
  </div>
  // this will be placed at the top after being processed
  <div>
    <dt>...</dt>
    <dd><button>Some button</button></dd>
  </div>
</dl>