title: UICollectionView viewForSupplementaryElementOfKind called three times
body: <p>I've a <code>UIViewController</code> with a <code>UICollectionView</code> attached on it. The problem is that <code>viewForSupplementaryElementOfKind</code> is called three times and not just one like in <code>UITableView</code>.</p>
  
  <p>Ideas ?</p>