Signed-off-by: Adam Vandenberg <flangy@gmail.com>
Fixes Homebrew/homebrew#480. Fixes Homebrew/homebrew#321.
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.
We don't install zenmap as it uses Python dist tools and doesn't play nice.