Invalidate layouts more aggressively when transitioning with animation (#476)

* Be more aggressive at invalidating layouts during transitions, add a debug method, fix some build errors when verbose logging

* Add a changelog entry

Source/ASDisplayNode.h

@@ -584,6 +584,11 @@ extern NSInteger const ASDefaultDrawingPriority;
  */
 - (NSString *)displayNodeRecursiveDescription AS_WARN_UNUSED_RESULT;
 
+/**
+ * A detailed description of this node's layout state. This is useful when debugging.
+ */
+@property (atomic, copy, readonly) NSString *detailedLayoutDescription;
+
 @end
 
 /**