first attempt at API-only nonrandom tests of BMInterface

* Partially addresses #426 but does not fix it
* Jenkins: http://jenkins.buttonweavers.com:8080/job/buttonmen-cgolubi1/347/

This pull adds a non-random override of `bm_rand()` for use with vagrant and with jenkins, and a new class, BMInterfacePublicTest.php, which tests BMInterface methods by calling and examining public methods only.  I started with three example scenarios, one with option dice, one with swing dice, and one with game continuations and chat.

I plan to add more tests to increase BMInterface coverage further and hit some more scenarios, but i wanted to push this now so we can try out the new regression tests against other pulls, and so that y'all can make sure you have an easy way to override `bm_rand()` wherever you are doing phpunit testing in your own MAMP stacks.