Add some login for atlasc of iOS 7 Sprite Kit

Hi, Mokagio!

First of all thanks to your dedication.

I just add the logic for processing with atlas from iOS 7 Sprite Kit.

I add 'Ninja Shinobi' image for ninja_shinobi.atlas from http://www.36peas.com/blog/2010/9/13/free-japanese-ninja-shinobi-sprite-sheet.html.
They are under 'Creative Commons attribution license'.

Please accept my pull request.

Regards,
Henry Kim
Alterant, Inc