Added Bandit BLA implmentation

********* PEOPLE *************
Primary reviewer: @sc932 

Reviewers: @suntzu86 

********* DESCRIPTION **************
Branch Name: norases_373_bla_bandit
Ticket(s)/Issue(s): Closes #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 would this require two versions of all those other things? A BernoulliArm would be a SampledArm so you can use it anywhere a SampledArm goes. BernoulliArm would just override validate and init to add in the specialized conditions on "loss".

unless i'm missing something huge, the object will behave exactly like it does right now.