Add windows compatibility

Test results on win before the patch: https://gist.github.com/stefanschneider/336772c69b661ebce60b
Test results on win after the patch: https://gist.github.com/stefanschneider/336772c69b661ebce60b

I had to fix this because the executor would not archive packages properly on windows. Windows related issue for executor: https://github.com/cloudfoundry-incubator/executor/issues/8