Added Bandit UCB1-tuned implementation

********* PEOPLE *************
Primary reviewer: @sc932 

Reviewers: @suntzu86 

********* DESCRIPTION **************
Branch Name: norases_366_ucb1_tuned_bandit
Ticket(s)/Issue(s): #366  

********* TESTING DONE *************
make test
make style-test
At the moment, only UCB1-tuned can deal with variance, right? We should be more explicit about this in docs... although I'm not 100% sure where is best. @sc932 ?

In the colander schema, it might be nice to fail if you specify variance and NOT UCB1-tuned. Or have a separate SampleArmWithVariance that subclasses this class? again @sc932 ?