第一步
Xcode --> File --> Target --> Application Extension --> Today Extension
第二步
参考教程：
http://www.jianshu.com/p/a66ed374a91c
http://www.jianshu.com/p/ca3e11d7686c
遇到的问题：
1、[_NCWidgetExtensionContext openURL:completionHandler:]_block_invoke failed: Error Domain=NSOSStatusErrorDomain Code=-10814 "(null)"
2、Embedded binary is not signed with the same certificate as the parent app. Verify the embedded binary target's code sign settings match the parent app's
解决方案：
1、主App里的URL Types 设置错误，或者没有设置
2、Today Extension证书没有创建，需要创建
