Add `res`

`res` is a small script that facilitates switching between screen
resolutions super quickly and easily.
Update gitconfig to use osxkeychain for OSX and cache for other systems
Merge pull request #96 from snichme/git_cred

Update gitconfig to use osxkeychain for OSX and cache for other systems
Merge remote-tracking branch 'upstream/master'

Conflicts:
	git/gitconfig.symlink.example