Deployment improvements

Replace deploy.sh with deploy.py
Some updates to setup scripts, for more consistency
Split out some common unix setup tasks into a script that both mac and
linux scripts call.

setup_unix_common.sh

@@ -0,0 +1,8 @@
+#!/usr/bin/env bash
+set -euo pipefail
+
+python3 $HOME/.dotfiles/deploy.py
+
+git clone https://github.com/hlissner/doom-emacs ~/.emacs.d
+~/.emacs.d/bin/doom install
+~/.emacs.d/bin/doom sync