Make Cell Node Properties Atomic (#74)

* Make ASCellNode indexPath and supplementaryElementKind atomic

* Update the change log

* Fix licenses

* Be explicit with atomic

* Rename the protocol

* And the file

Source/ASRangeManagingNode.h

@@ -0,0 +1,35 @@
+//
+//  ASRangeManagingNode.h
+//  Texture
+//
+//  Copyright (c) 2017-present, Pinterest, Inc.  All rights reserved.
+//  Licensed under the Apache License, Version 2.0 (the "License");
+//  you may not use this file except in compliance with the License.
+//  You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+
+#import <Foundation/Foundation.h>
+#import <AsyncDisplayKit/ASTraitCollection.h>
+
+@class ASCellNode;
+
+NS_ASSUME_NONNULL_BEGIN
+
+/**
+ * Basically ASTableNode or ASCollectionNode.
+ */
+@protocol ASRangeManagingNode <NSObject, ASTraitEnvironment>
+
+/**
+ * Retrieve the index path for the given node, if it's a member of this container.
+ *
+ * @param node The node.
+ * @return The index path, or nil if the node is not part of this container.
+ */
+- (nullable NSIndexPath *)indexPathForNode:(ASCellNode *)node;
+
+@end
+
+NS_ASSUME_NONNULL_END