The traceur transpiler is nice and full-featured, but it has some major

problems with recent chrome updates. This change switches us over to the babel

transpiler, which means we're using the same es6 implementation on both the

backend and frontend.
Babel is unfortunately missing a couple Array features (Array.from and

Array.find), and the handling of this in fat-arrow functions is slightly

different. Babel's handling of this is actually more correct than traceur.

Babel also has more strict rules regarding super() calls in class

constructors. The bulk of this change is cleaning up those issues.

Flipped around between the calendar and user detail views. Everything seemed to

work correctly. Deployed and saw that everything worked correctly in production

too.