Send message if Transmission goes down

[JNat]

If Transmission goes down for some reason after the bot's running, we get no hint of it. Furthermore, interacting with the bot just generates error messages instead — not very user friendly ones, more developery-facing ones :)

Might be a good idea to have the bot let you know if Transmission goes down (also, if it then goes up again, it could let you know of that).