Added Bandit BLA implmentation

********* PEOPLE *************
Primary reviewer: @sc932 

Reviewers: @suntzu86 

********* DESCRIPTION **************
Branch Name: norases_373_bla_bandit
Ticket(s)/Issue(s): #373 

********* TESTING DONE *************
make test
make style-test

Bug fixed:
variance in a sample arm is dropped in _make_bandit_historical_info_from_params
if you're saving/restoring rng state, then should get rid of the seed stuff in this class; that was the main point of the change. In doing so, you can set the seed once at the top of your test and get a totally deterministic run.

@sc932 just tested, I don't believe the rng is global at the class/file level. I think it's global across everything. docs don't really say much about it, although given the way imports work i think it'd be quite difficult to do this at a per-file or per-class level.