* Initial commit to move [ASLayoutSpec children] from std::map to NSMutableArray
* Add NSFastEnumeration to ASLayoutable
* ASNullLayoutSpec is a Singleton now
* Move ASLayoutSpecPrivate in Private folder
* Move to NSArrayPointer and remove ASNullLayoutSpec
* Revert "Move to NSArrayPointer and remove ASNullLayoutSpec"
This reverts commit 9ab9cf7024b1f6e1984d84fe58af2b84e84cdf94.
* Move to childAtIndex: and setChild:atIndex: