Use babel to run ES6 on the server.
Review Request #7246 — Created April 23, 2015 and submitted — Latest diff uploaded
We already have ES6 on the client courtesy of traceur, but not on the server.
Babel provides a node wrapper that will precompile everything, allowing much
of the server-side code to use handy features like let and arrow functions.
Verified that everything still works on both dev and production.