dyld: Library not loaded: /Syste

dyld: Library not loaded: /System/Library/Frameworks/UserNotifications.framework/UserNotifications

Referenced from: /var/containers/Bundle/Application/B0936ED2-FB82-4487-AE21-A1185AA36EF9/TestUserNotification.app/TestUserNotification

Reason: image not found

Xcode8 引用UserNotifications.framework，在iOS9.3 报错；

高版本Framework不支持低版本手机，改为可选即可