title: UICollectionView constraints doesn't allow to scroll
body: <p>I'm expecting an issue with my <code>UICollectionView</code>, basicallly when I clear the constraints it scrolls perfectly though I can't reach the bottom (but that's another day's matter), however the width is way too big, I only see the left half of my <code>UICollectionView</code>.</p>
  
  <p>Now, when I set my <code>constraints</code> to make it fit the screen, it won't scroll anymore. Even the <code>UIRefreshControl</code> isn't triggered.</p>
  
  <p>I ran out of ideas, does somebody have a clue? or a solution?</p>
  
  <p>Thanks a lot!</p>
  
  <p><strong>Edit:</strong>
  It doesn't scroll though it bounces... </p>