Feature Request: !offline allows you to turn others off #33
Description
Summary
A feature that allows one TA to turn another TA to offline status, in case they forget.
Use could be !offline "user ID" or "username"
Basic example
Avery forget to go !offline at the end of the session. Jack wants to set everyone to offline by 10:00pm so that everyone knows that the TAs are off.
Jack: !offline @Avery
Motivation
It would be annoying to have a TA left online when they are no longer online.