Shorten is a shell script that generates shortened GitHub urls using Git.io. It takes two arguments: the first is the GitHub url to be shortened (e.g. https://github.com/gmal1), and the second optional argument is a string for the vanity url (e.g. https://git.io/somevanityurl). Without the second argument, the url will be auto-generated for you.
cecho function borrowed from @nnja.