title: UICollectionView with two headers
body: <p>Having two headers in UICollectionView?</p>
  
  <p>I've got a UICollectionView which uses the flow layout, which also has a header and footer:</p>
  
  <pre><code>---------   
  | head  |
  ---------
  | A | B |
  ---------
  | C | D |
  ---------
  | foot  |
  ---------
  </code></pre>
  
  <p>Occasionally, I'd like to have two headers, like so:</p>
  
  <pre><code>---------   
  | head1 |
  ---------   
  | head2 |
  ---------
  | A | B |
  ---------
  | C | D |
  ---------
  | foot  |
  ---------
  </code></pre>
  
  <p>I'm stuck on how to achieve this. The flow layout only appears to allow one head and one foot. How can I add a second header?</p>
  
  <hr>
  
  <p>edit: I have also implemented sticky headers - <a href="http://blog.radi.ws/post/32905838158/sticky-headers-for-uicollectionview-using" rel="noreferrer">http://blog.radi.ws/post/32905838158/sticky-headers-for-uicollectionview-using</a> - but I only want the first header to be sticky. This is why I can't just include everything in one header.</p>