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
Have you run ```make -B docs``` and looked over your rendered doc pages? You should do this.

My experience has been that math, dicts, pseudocode, etc. all read more nicely if wrapped in at least double backticks if not at math-block, e.g.,
```
the thing, ``{win:10, lose:10, ...}`` is cool
```