 private let defaultMarginOfCells = CGFloat(2)
 private let defaultThresholdOfZoom = CGFloat(0.5)
 
-// MARK: ResizableCollectionViewDelegate
+// MARK: - ResizableCollectionViewDelegate
 public protocol ResizableCollectionViewDelegate : UICollectionViewDelegate {
     
     func willPinchIn(collectionView: ResizableCollectionView)

    
}

// MARK: ResizableCollectionViewDataSource
public protocol ResizableCollectionViewDataSource : UICollectionViewDataSource {
    
    func minNumberOfCellsInLine(collectionView: ResizableCollectionView) -> Int

    
}

// MARK: - ResizableCollectionViewDelegate - default implementation
extension ResizableCollectionViewDelegate {
    
    func willPinchIn(collectionView: ResizableCollectionView) {
