Add support for channel selection to playbot
Add support for channel selection to playbot

This also removes the awkward passing of nicknames to determine whether
to use a template or not.

It introduces two new keys into the configuration file.
My current irc.yaml looks like this:

- nickname: "playbot-dev"
  server: irc.mozilla.org
  port: 6667
  channels:
    - "#rust"
  keys: [null, "hunter2"]
  password: abc123abc
  triggers:
    - [ "playbot:(.*)", "stable", True ]
    - [ "rusti:(.*)", "stable", True ]
    - [ "playbot-mini:(.*)", "stable", False ]
    - [ "rusti-mini:(.*)", "stable", False ]
    - [ ">>(.*)", "stable", True ]
    - [ "n\s*>>(.*)", "nightly", True ]
    - [ "nightly\s*>>(.*)", "nightly", True ]
    - [ "b\s*>>(.*)", "beta", True ]
    - [ "beta\s*>>(.*)", "beta", True ]
    - [ "s\s*>>(.*)", "stable", True ]
    - [ "stable\s*>>(.*)", "stable", True ]

plietar/pony-playpen,rust-lang/rust-playpen,rust-lang/rust-playpen,plietar/pony-playpen,tilpner/rust-playpen,tilpner/rust-playpen,tilpner/rust-playpen,rust-lang/rust-playpen,rust-lang/rust-playpen,plietar/pony-playpen,plietar/pony-playpen,tilpner/rust-playpen