Add the initial implemenation of my pairing script

* Let's you add, remove, and list users for the $TMUX_USER account on
  your computer by using https://github.com/chrishunt/github-auth
* You can kick off a shared tmux session
* You can start up the reverse tunnel using https://ngrok.com
* See `pair --help` for usage
Remove "pair" alias

* replaced by bin/pair
Add gemfile for my environment

* This will allow me to bundle dependencies I use a lot. e.g. hitch
Don't track Gemfile.lock

* For now, I assume I'll want to bundle the newest versions of these
  gems for new environments.
Add hitch function to zshrc

* This is a slightly modified form of the script output by `hitch -s`
* See https://github.com/therubymug/hitch
Add aliases for hitch commands

* hu - hitch up
* uh - unhitch
Add alias for common pair