Added assertion & documentation update

Author: CezaryKopacz

.DS_Store

@@ -1,11 +1,11 @@
 Pod::Spec.new do |s|
   s.name         = "CKWaveCollectionViewTransition"
-  s.version      = "1.0.0"
+  s.version      = "1.0.1"
   s.summary      = "Wave like transition between two or more collection view."
   s.homepage     = "https://github.com/CezaryKopacz/CKWaveCollectionViewTransition"
   s.license      = { :type => "MIT" }
   s.author       = { "Cezary Kopacz" => "salvation.sv@gmail.com" }
-  s.source       = { :git => "https://github.com/CezaryKopacz/CKWaveCollectionViewTransition.git", :tag => "1.0.0" }
+  s.source       = { :git => "https://github.com/CezaryKopacz/CKWaveCollectionViewTransition.git", :tag => "1.0.1" }
   s.source_files  = "Classes", "Classes/**/*.{swift}"
   s.ios.deployment_target = "8.0"
 end

CKWaveCollectionViewTransition.podspec

@@ -234,6 +234,8 @@ class CKWaveCollectionViewAnimator: NSObject, UIViewControllerAnimatedTransition
     }
 
     private func enumerateVisibleCellsAndAddAnimations(destinationPoint: CGPoint, sourceCollectionViewController: UICollectionViewController, destinationCollectionViewController: UICollectionViewController) {
+
+        assert(destinationCollectionViewController.selectedIndexPath != nil, "Forgot to set selectedIndexPath property?")
 
         var sourceIndexPathsForVisibleCells = sourceCollectionViewController.collectionView?.indexPathsForVisibleItems() as? Array<NSIndexPath>
         sourceIndexPathsForVisibleCells!.sort({ $0.row < $1.row })

Classes/CKWaveCollectionViewAnimator.swift

@@ -48,8 +48,17 @@ func navigationController(navigationController: UINavigationController, animatio
     }
 ```
 
+ * The last thing you have to set is self.selectedIndexPath property in your didSelectItemAtIndexPath method implementation.
 
 
+```swift
+override func collectionView(collectionView: UICollectionView, didSelectItemAtIndexPath indexPath: NSIndexPath) {
+        
+        self.selectedIndexPath = indexPath
+...
+
+}
+```
 
 
 ## Properties