title: Change UICollectionViewCell size on different device orientations
body: <p>I am using an <code>UICollectionView</code> with <code>UICollectionViewFlowLayout</code>.</p>
  
  <p>I set the size of each cell through the </p>
  
  <pre><code>collectionView:layout:sizeForItemAtIndexPath:
  </code></pre>
  
  <p>When switching from portrait to landscape, I would like to adjust the size of each cell to completely fit the size of the CollectionView, without leaving padding space between cells.</p>
  
  <p>Questions:</p>
  
  <p>1) How to change the size of a cell after a rotation event?</p>
  
  <p>2) And, even better, how to make the layout where the cells always fit the entire size of the screen?</p>