Added Bandit epsilon-greedy implementation

********* PEOPLE *************
Primary reviewer: @sc932

Reviewers: @suntzu86

********* DESCRIPTION **************
Branch Name: norases_255_create_epsilon_greedy_bandits
Ticket(s)/Issue(s): Closes #255 

********* TESTING DONE *************
make test-no-tox
make style-test-no-tox
1. This class actually is not a full implementation of BanditInterface b/c you do not override all abstractmethods. You cannot instantiate ```eps = Epsilon()```

2. You might consider renaming this to ```EpsilonBandit``` and the subclass to ```EpsilonGreedyBandit``` or thereabouts. epsilon is a really generic name