title: UICollectionView inside UIScrollView not scrolling
body: <p>I have a vertically-scrolling scroll view that has a single subview. This subview has a couple of collection views. I want them to scroll horizontally. It doesn't work because they are inside the scroll view.
  The problem is that the pan/scrolling gesture is working just for the scroll view and it doesn't propagate to the collection views. I just see the scroll view scrolling.
  There is the same problem with tapping on a collection cell. This event just doesn't happen.</p>
  
  <p>I already tried adding the gestures manually but I am not able to scroll the collection views.</p>
  
  <p>How can I propagate all the gestures ?</p>
  
  <p>Thank you !</p>
  
  <p><img src="https://i.stack.imgur.com/Ufion.png" alt="[See Storyboard Image">]<a href="https://i.stack.imgur.com/Ufion.png" rel="nofollow noreferrer">1</a></p>