add workflow stress test

[bacongobbler]

cross-post of https://github.com/deis/deis/issues/4037

@jchauncey has found some interesting problems when running significant load through deis. I'd like to see an automated version of this test (or similar) so that we can watch deis' performance over the course of future releases. We could even run this on the various providers and compare performance. :smile: