~/.aliases: b=firefox.
~/.aliases: shortcuts for university.
~/.env: ruby 2.1.0 is the current ruby.
~/.mailcap: handle pdfs with evince.

xdg-open seems unreliable, various apps install their own handlers. is
there a reliable way to configure xdg-open with a text file?
~/.zshrc: use config for opam/ocaml.