Changing time zone shouldn't change reminder time
I'm not sure if it's related to #46. Feel free to merge if that is so.
I set a reminder at 7pm when I was at GMT and now I moved to GMT+2 I got the notification at 9pm.
I think it would be more meaningful if the notification followed a person's schedule rather than abstract time zones. I don't think I would get up to exercise at e.g. 2am if I moved to GMT+7.