While the offset was working, the last message ID was never reset,
so it would always pick an higher message ID (safety check), which
completely defeated the purpose of negative time offsets. Should
close#496.
Telegram would refuse to reply any further unless the message ID
had the correct time (causing some behaviour like .connect()
never connecting, due to the first request being sent always
failing). The fix was to use time_offset when calculating the
message ID, while this was right, it wasn't in use.