Brew-publish NPM

brew-publish

Updates the given Homebrew formula version and sends a pull request with the change.

Originally authored by @mislav, this utility was extracted from ruby-build's scripts. The brew-publish script itself has not been modified. In addition to extracting the script to its own repo, a package.json has been added so it can be installed via npm. (There is no intention of publishing the script to npm. Rather, it can be installed via github URL.)