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
i want to check that we have cases where:

1. num_winning_arms == num_arms > 1

2. num_arms > num_winning_arms > 1

to exercise all the code paths