Fix unit test runner

I work at Facebook on the HHVM Language and Tools team. Beatbox is some of the only open source code I know of that is extensively using some of our unannounced HHVM extensions, notably extended type annotations and async functions. Having a second codebase to play with beyond Facebook's www stack is really useful for what I'm doing right now. I'm going to be doing a little more mucking with beatbox and want at least a smoke test that what I'm doing is reasonable, so having a working test runner would be really useful to me :)

I see this is sync'd from an upstream SVN repo, so let me know if a github pull request isn't your preferred way to take patches.

I'm on IRC in #hhvm as "jwatzman|work" during PST work hours if you want to grab me there as well!