Introduces `git_template` for `git init` templating

Inspired by http://tbaggery.com/2011/08/08/effortless-ctags-with-git.html

* Runs `ctag` on `commit` / `branch` / `checkout`
* Extensible via `~/.git_template.local/hooks/{pre,post}-*`
I'm curious about when this alias would be useful to run manually, or is it just for the post hooks?