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
why does a bernoulli arm have to have loss = 0.0 exactly? also isn't loss an integer?

Seems to me like it'd make sense for BernoulliArm to be a separate class since it's behavior is pretty different to that of a SampleArm