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
nit: probably not worth fixing now, but in python it's more std to write "dict" and "str" as those are the actual names of the types. String() isn't a thing afaik.