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
why do you need __eq__?

__eq__ seems like a somewhat complex issue. going based on the responses here: http://stackoverflow.com/questions/390250/elegant-ways-to-support-equivalence-equality-in-python-classes
your implementation is incomplete. you don't have a neq, this breaks on inheritance, and this may or may not work for sets depending on what __hash__ does (idk, you should verify).

There's also nicer ways to check the equality of fields with slots; in particular you can check self.__slots__ and then check values:
http://stackoverflow.com/questions/4522617/equality-of-python-classes-using-slots?lq=1
idk if that's the best way but it is a way. i'd do some more searching.