Previous version didn't compile on Snow Leopard.
TODO: Enable Guile support if requested, or if Guile has previously
been installed. I'll leave it for any Guile users out there to provide
a patch.
brewkit.rb changes ENV destructively, so lets not do that everytime a formula
is required. Now it's possible for other tools to require a formula
description without worrying about side-effects.
Adam Vandenberg
Max Howell
Hunter Morris