Create macchanger.rb

This is the formulae for macchanger 0.2. With that, you could understand how MAC filtering works and how to better protect your WiFi network against hackers. Well known package on GNU/Linux. I would love to have this one on Homebrew.

Related to this guy: https://github.com/acrogenesis/macchanger
Can a test be added to do something more substantial then e.g. `--version` or `--help`? See `cmake.rb` for an example of a formula with a good test. Thanks!