Fix naming convetion:

- "Layout node" is changed to "layout spec".
- Update tests.
- Update Kittens sample.

AsyncDisplayKit/Layout/ASStaticLayoutSpec.h

@@ -0,0 +1,46 @@
+/*
+ *  Copyright (c) 2014-present, Facebook, Inc.
+ *  All rights reserved.
+ *
+ *  This source code is licensed under the BSD-style license found in the
+ *  LICENSE file in the root directory of this source tree. An additional grant
+ *  of patent rights can be found in the PATENTS file in the same directory.
+ *
+ */
+
+#import <AsyncDisplayKit/ASLayoutSpec.h>
+#import <AsyncDisplayKit/ASStaticLayoutSpecDimension.h>
+
+@interface ASStaticLayoutSpecChild : NSObject
+
+@property (nonatomic, readonly) CGPoint position;
+@property (nonatomic, readonly) id<ASLayoutable> layoutableObject;
+
+/**
+ If specified, the child's size is restricted according to this size. Percentages are resolved relative to the static layout spec.
+ */
+@property (nonatomic, readonly) ASRelativeSizeRange size;
+
++ (instancetype)newWithPosition:(CGPoint)position layoutableObject:(id<ASLayoutable>)layoutableObject size:(ASRelativeSizeRange)size;
+
+/**
+ Convenience with default size is Unconstrained in both dimensions, which sets the child's min size to zero 
+ and max size to the maximum available space it can consume without overflowing the spec's bounds.
+ */
++ (instancetype)newWithPosition:(CGPoint)position layoutableObject:(id<ASLayoutable>)layoutableObject;
+
+@end
+
+/*
+ A layout spec that positions children at fixed positions.
+
+ Computes a size that is the union of all childrens' frames.
+ */
+@interface ASStaticLayoutSpec : ASLayoutSpec
+
+/**
+ @param children Children to be positioned at fixed positions, each is of type ASStaticLayoutSpecChild.
+ */
++ (instancetype)newWithChildren:(NSArray *)children;
+
+@end