iOS8 之后添加了App Groups，应用可以通过App Groups共享数据，原文如下：
AppGroup allows data sharing between two different apps or even app and widgets by creating one common shared path (like document directory). Data saved over there can be accessed by any app which is associated with that particular AppGroup. It is an offline data sharing between apps.
使用方法如下：
1.创建app groups
2.配置app groups
3.使用
在代码中定义创建的app group
通过NSUserDefaults 共享数据
