参考：
1、http://troybrant.net/blog/2010/01/in-app-purchases-a-full-walkthrough/
2、http://iosdeveloper.diandian.com/post/2011-08-26/4366441
参考：
1、http://troybrant.net/blog/2010/01/in-app-purchases-a-full-walkthrough/
2、http://iosdeveloper.diandian.com/post/2011-08-26/4366441