title: Placing a margin around each edge of the UICollectionView
body: <p>When the UICollectionView is populated with items they always go right to the edges of the UICollectionView like so:</p>
  
  <pre><code>---------------
  |X X X X X X X|
  |X X X X X X X|
  |X X X X X X X|
  |X X X X X X X|
  |X X X X X X X|
  |X X X X X X X|
  ---------------
  </code></pre>
  
  <p>I would like to place a margin around each edge like so:</p>
  
  <pre><code>---------------
  | X X X X X X |
  | X X X X X X |
  | X X X X X X |
  | X X X X X X |
  | X X X X X X |
  | X X X X X X |
  ---------------
  </code></pre>
  
  <p>I tried to achieve this by placing the UICollectionView inside its hosting UIView by setting its Frame to simulate a border but it scrolls within the Frame so gets cut off at the top and bottom and the scroller also appears in the bounds of the frame.</p>
  
  <p>I have looked at the API but I cannot see anything obvious to achieve this. Any ideas?</p>