http://blog.csdn.net/totogo2010/article/details/8205810
Auto Layout相关：网站也不错。take a care。
http://www.raywenderlich.com/zh-hans/22873/ios-6-%E8%87%AA%E5%8A%A8%E5%B8%83%E5%B1%80-%E5%85%A5%E9%97%A8%EF%BC%8D1
