Move git-related executables into git role
Use tagged roles to control what's installed
Add lein executable to Clojure role
Add heroku executables to Heroku role
Move Emacs executables into Emacs role

- Symlink `emacsclient` into ~/.bin
- Transfer `emacsserver` from [jcf/prezto][]

[jcf/prezto]: https://github.com/jcf/prezto
Move `relx` into Erlang role
Add `gctags` to Emacs role
Move over remaining executables from Prezto