Version 0.4.0: The Glory of Zombie Omega

Backwards Compatibility Breakers

This update majorly changes the standard API of this library. The factory classes are the primary entrypoint now and the old classes just house behavior to use the commands. PHP 5.4 is now a requirement, as is the usage of nubs/which for locating commands in the user's PATH. The result of all this is something much more extensible (eventually for adding Windows Support) and something that has fully configurable behaviors.