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 might've also considered the way @sc932 set up the different "next_points" endpoints (EPI, kriging, constant liar). There we had separate files for each endpoint and separate Request schemas (so that the hyperparameterinfo struct type doesn't have to be decided at runtime). That way is perhaps more clear but certainly more verbose.

@sc932 thoughts?