Merge pull request #11 from zwang/master

resolve compile warning about variable never read

Chatto/Source/ChatController/ChatCollectionViewLayout.swift

@@ -84,7 +84,10 @@ public class ChatCollectionViewLayout: UICollectionViewLayout {
         dispatch_async(dispatch_get_global_queue(DISPATCH_QUEUE_PRIORITY_DEFAULT, 0)) { () -> Void in
             // Dealloc of layout with 5000 items take 25 ms on tests on iPhone 4s
             // This moves dealloc out of main thread
-            oldLayoutModel = nil
+            if oldLayoutModel != nil {
+                // Use nil check above to remove compiler warning: Variable 'oldLayoutModel' was written to, but never read
+                oldLayoutModel = nil
+            }
         }
     }