Cleanup 'empty' rooms.

[Half-Shot]

One of the tricky problems we have is to be able to tell when a room is effectively wasting resources. It would make sense to stop sending events to rooms with no matrix users, and possible discussion around withholding events from rooms with inactive users (although, that's a whole different story).

[Half-Shot]

The new plan is to periodically call ASBot.getMemberLists() and check to see if users are active in there. If not, we 'disconnect' them if they are connected and check again later. Seems like a good idea to do this every 5 minutes.

[Half-Shot]

https://github.com/matrix-org/matrix-appservice-bridge/pull/45 will make this eeeasy :)

[Half-Shot]

Aaaaaaand #83 is the actual PR that will do this