title: Add a simple UIView as header of UICollectionView
body: <p>I have a <code>UICollectionView</code>. I would like to add a header. My header would only be a <code>UILabel</code>. I've :</p>
  
  <p>1) selected "Section Header" as a Collection View accessory in the IB.</p>
  
  <p>2) created a Collection Reusable View in the IB, on the side, declared as <code>collectionViewHeader</code>.</p>
  
  <p>3) added those lines :</p>
  
  <pre><code>- (UICollectionReusableView *)collectionView:(UICollectionView *)collectionView viewForSupplementaryElementOfKind:(NSString *)kind atIndexPath:(NSIndexPath *)indexPath
  {
      if (kind == UICollectionElementKindSectionHeader) {
  
              return collectionViewHeader;
      }
      return nil;
  }
  </code></pre>
  
  <p>But they are never called.</p>
  
  <p>Do I have to create a class just for that label in order to use </p>
  
  <pre><code>[self.collectionView registerClass:[UICollectionReusableView class] forSupplementaryViewOfKind:UICollectionElementKindSectionHeader withReuseIdentifier:@"header"];
  </code></pre>
  
  <p>?</p>
  
  <p>Why isn't it as simple as the <code>UITableView</code> where you just drag and drop whatever header you want ?! Things are so complicated with <code>UICollectionView</code>...</p>