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.
Installs as $prefix/bin/gsed, like the Macports version. This
makes it easier to alias so that you don't have to put $prefix/bin
ahead of /usr/bin in your $PATH.
Adam Vandenberg
Mike McQuaid
Gabriele Sales
Max Howell
Joe Shaw