Bugfix - If a header precedes a section, move it inside the secton

[jenweber]

I came across this while working on the website redesign.

Before

<h2 id="some-title">Some title</h2>
<section aria-labelledby="some-title">
  <p>Ember is doing better at accessibility</p>
<section>

After

<section aria-labelledby="some-title">
  <h2 id="some-title">Some title</h2>
  <p>Ember is doing better at accessibility</p>
<section>

[MelSumner]

Perfect! 👍

[MelSumner]

@jenweber how do we re-run these tests?

[jenweber]

I think the easiest thing to do is to rebase the branch. I can do that!

[MinThaMie]

Closed in favour of #159