Update TMXGenerator to support tile flipping.

[psineur]

http://www.cocos2d-iphone.org/forum/topic/28401#post-141024

It uses fixes in cocos2d-iphone 1.1 beta2+ ( "develop" branch ).
Currently extensions uses last stable version of cocos2d-iphone 1.0
I think next version of extensions must be released after cocos2d-iphone 1.1 stable, but in develop branch - we can use develop branch of cocos2d-iphone.