instruments的资料，内存泄漏

http://blog.youkuaiyun.com/totogo2010/article/details/8233565

http://www.cnblogs.com/zilongshanren/archive/2011/08/08/2131140.html

http://www.raywenderlich.com/23037/how-to-use-instruments-in-xcode

http://developer.apple.com/library/mac/#documentation/DeveloperTools/Conceptual/InstrumentsUserGuide/Introduction/Introduction.html