ENH: Allows to add rooms by specifying a string

[quazgar]

There's also a new keyword arg for MatrixBotAPI: exclusive_rooms=True tells only the specified rooms should be used, all others will be left.

[mrdumpty]

Look at my PR, its logic is slightly better. If rooms specified, bot will be exclusive anyway. If not specified, bot will be listening on all of its rooms. Accept invites is the separated option.

[shawnanastasio]

Hi @quazgar, thanks for the PR (and sorry for the late response)!

I think the ability to specify rooms by ID string is a useful feature, and your implementation looks good to me.

I'm not sure about the usefulness of the exclusive_rooms functionality you've added, though. Could you maybe explain the rationale for adding it? There's some discussion in PR #18, but it seems that its usefulness is limited, since users can already restrict which rooms the bot is active in with the rooms parameter.