title: UICollectionView doesn't bounce when datasource has only 1 item
body: <p>I have a UICollectionView with a custom UICollectionViewFlowLayout. It scrolls horizontally and only shows one item at a time (full height). I have pagingEnabled = YES so that it sticks to pages. </p>
  
  <p>The UICollectionView shows photos within a particular day. I initially had buttons to change the day +/- 1 day, but I thought it would be neat if the user could pull on the collection view past the first or last image (past a predetermined threshold) to change the day. I implemented this using the UIScrollView delegate methods and it works great...... if there are 2 or more items in the collection view. </p>
  
  <p>This is hard to describe, but if there is only 1 item, it doesn't allow me to pull the item past it's bounds. I.E. there is no bounce to it. </p>
  
  <p>I'd like to have this behavior, but I need to overcome this problem first. I'm thinking that if I removed pagingEnabled = YES and used targetContentOffsetForProposedContentOffset:proposedContentOffset:withScrollingVelocity, that I may be able to get it to work but I really enjoy the snappy behavior that paging enables. (They are mutually exclusive). </p>
  
  <p>Any ideas on this?</p>