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.
Unfortunately, dealing with them requires quite a bit of shell configuration.
I offered the best documentation of this configuration that I could, but it’s
fairly verbose and a bit repulsive… unfortunately, the other option (attempting
to preform the setup automatically) turns out to be even messier, and prone to
mistakes to boot.
