Add windowless client

[jrick]

This feature request is admittedly pretty out there but i'm not to enthralled with the idea of needing a separate tmux window just for zkc. In my perfect world, I could run zkclient without any UI, and instead interact with it from an irssi plugin or any other frontend.

Given the differences between irc and zkc's protocol I don't expect this to be a walk in the park, but I have used non-irc protocols from irssi plugins in the past (e.g. xmpp through bitlbee) and have been pretty happy with the results.

[marcopeereboom]

I super want this. I even have ideas. Anyone interested in working on this with me?