hubot: Add a hubot image

hubot: Add a hubot image

I had to instal Git to avoid a:

  GET https://registry.npmjs.org/scoped-http-client
   GET https://registry.npmjs.org/async
  ERR! not found: git
  npm ERR!
   ERR! Failed using git.
   This is most likely not a problem with npm itself.
   Please check if you have git installed and in your PATH.

   Linux 3.13.0
  command "/usr/bin/node" "/usr/bin/npm" "install"
  cwd /hubot
  node -v v0.10.21
   1.3.11
   ENOGIT

error during the 'npm install'.  Other than that, this is fairly
straightforward, although I wish that the script dependencies were
handled automatically :p.

Docker doesn't let you modify /etc/hosts at the moment [1].  If you
need to add custom DNS (because your target IRC server doesn't resolve
automatically), you can use dnsmasq [2].  I added something like this
to the tail of my hubot/Dockerfile.template:

  RUN emerge -v dnsmasq
  RUN rc-update add dnsmasq default
  RUN echo 'address="/irc.example.net/192.168.0.2"' >> /etc/dnsmasq.conf
  RUN echo 'nameserver 192.168.0.1' >> /etc/resolv.dnsmasq.conf
  RUN echo 'resolv-file=/etc/resolv.dnsmasq.conf' >> /etc/dnsmasq.conf
  RUN echo 'listen-address=127.0.0.1' >> /etc/dnsmasq.conf
  RUN sed -i 's/need localmount net$/use localmount net/' /etc/init.d/dnsmasq

And fired up the container with:

  docker run ... --dns 127.0.0.1 wking/hubot /bin/bash
  # rc default
  # cd hubot
  # REDISCLOUD_URL="${REDIS_PORT}" exec bin/hubot --name "${HUBOT_IRC_NICK:-hubot}" -a irc

[1]: https://github.com/dotcloud/docker/issues/2267
[2]: https://github.com/dotcloud/docker/issues/1951#issuecomment-24960347