Implement Epsilon-First bandit endpoint

********* PEOPLE *************
Primary reviewer: @sc932

Reviewers: @suntzu86

********* DESCRIPTION **************
Branch Name: norases_335_create_epsilon_first_bandit_endpoint
Ticket(s)/Issue(s): Closes #335

********* TESTING DONE *************
make test
make style-test
You can kill "In other words,"

We are trying to keep the style of the docs more declarative and less conversational in general.