Zombie cukes

This PR implements the smoke testing script as cucumber tests run in [zombie][]. It doesn't wrap cucumber or zombie in fibers, but I struggled to get cucumber+phantomjs wrapped in fibers (like in Aestimia) working here. Phantom would crash often and irregularly, complaining about not being able to start ghost driver after several tests had already passed... they were sad times, my friends.

This combo works beautifully though, at least on my local machine! I'm open to fiberizing this too, I just couldn't wrap my head around it.

Note also that this provides no means to run the automated smoke tests against staging or production, but they *would* get run on travis for each new pull request, which is a great start.

So @toolness, would you be able to live with this?

@threeqube, check out [this file](https://github.com/stenington/openbadges-validator-service/blob/7ae231390ca0b6f90fa24a4b3b356d50721bded5/features/smoke-test.feature) in particular, and let me know if the tests are meaningful to you, or if they could be improved. 

@andrewhayward, peruse at your own leisure and comment if you feel so inclined.

[zombie]: http://zombie.labnotes.org/