[iOS] iOS 8 Push Notification Service

iOS 8 為 Notification Center 帶來新功能，所以取得 token 的 api 也修改了，如下所示：

if(IS_IOS8)
{
    [[UIApplication sharedApplication] registerUserNotificationSettings:[UIUserNotificationSettings settingsForTypes:(UIUserNotificationTypeSound | UIUserNotificationTypeAlert | UIUserNotificationTypeBadge) categories:nil]];
    [[UIApplication sharedApplication] registerForRemoteNotifications];
}
else
    [[UIApplication sharedApplication] registerForRemoteNotificationTypes:(UIRemoteNotificationType)(UIRemoteNotificationTypeBadge | UIRemoteNotificationTypeSound | UIRemoteNotificationTypeAlert)];