iOS 远程推送注册的小问题

iOS8有了新方法，用新方法后，用7.0版本运行会奔溃。只要加一句判断就ok：

#ifdef __IPHONE_8_0
    // 在 iOS 8 下注册苹果推送，申请推送权限。
    
    UIUserNotificationSettings *settings = [UIUserNotificationSettings settingsForTypes:(UIUserNotificationTypeBadge
                                                                                         |UIUserNotificationTypeSound
                                                                                         |UIUserNotificationTypeAlert) categories:nil];
    [[UIApplication sharedApplication] registerUserNotificationSettings:settings];
#else
    // 注册苹果推送，申请推送权限。
    [[UIApplication sharedApplication] registerForRemoteNotificationTypes:UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeAlert | UIRemoteNotificationTypeSound];
#endif