Added Bandit UCB1 implementation

********* PEOPLE *************
Primary reviewer: @sc932 

Reviewers: @suntzu86 

********* DESCRIPTION **************
Branch Name: norases_354_ucb1_bandit
Ticket(s)/Issue(s): #354 

********* TESTING DONE *************
make test
make style-test
Can we make a constant for DEFAULT_UCB_SUBTYPE, so we can change it everywhere easily when we make other (or better) UCB methods?