Alias open to `xdg-open`
Promote git pair/unpair functions to scripts
Add tat script

Source:
<https://raw.githubusercontent.com/thoughtbot/dotfiles/d8003e654ef6d8b7901b57cf6b1118b70aa63cca/bin/tat>
Add git-churn script

Source:
<https://raw.githubusercontent.com/garybernhardt/dotfiles/fdf426f192d799a6dbbbffeb60ec29372fcca904/bin/git-churn>