Allow $EDITOR to be set up elsewhere

Conflicts:
	system/env.zsh
Fix syntax error
Don't show a version if rbenv can't switch to it
Fix seds treatment of tabs

Per https://github.com/holman/dotfiles/commit/3d2a856d2475f8c7e6cff6117652f92542cb6247#commitcomment-3561553.
Update gitconfig to use osxkeychain for OSX and cache for other systems
Turn syntax highlighting on by default in vim
Wrap on `git commit` descriptions

In descriptions like these, we should wrap according to how Git suggests
we break (72 characters).
Add a python/install.sh script

Ideally I want to just have one script/install script that runs ./install.sh in
every directory in my dotfiles. Then we have a loose framework to build up machines.
But I'm too lazy, so pulls accepted. :)
Auto run all install.sh scripts

This adds a ``script/install`` that iteratively runs all ``install.sh``
scripts located in the dotfiles directory. Solves @holman's request from
commit f697ba7
Remove todo.txt stuff
Add `todo`
Just use $*
Fixed syntax error
git-nuke
I just don't use `h`
Grab my real public key
Remove autocompletion for deleted `h` function
Show me my unpushed changes
Show me my unpushed changes diffstat
Include the count, too