useBuiltIns uses versions of the helpers that do not import even
internal polyfills from core-js.
useESModules uses versions of the helpers that do not go through
transform-es2015-modules-commonjs. This allows for smaller builds in
module systems like webpack, as it doesn't need to preserve commonjs
semantics.
This includes changes to the babel-runtime build-dist script, which
will build the versions of the runtime helpers to be used by
combinations of useBuiltIns and useESModules.
I'm extremely stupid and didn't commit as I go. To anyone reading this
I'm extremely sorry. A lot of these changes are very broad and I plan on
releasing Babel 6.0.0 today live on stage at Ember Camp London so I'm
afraid I couldn't wait. If you're ever in London I'll buy you a beer
(or assorted beverage!) to make up for it, also I'll kiss your feet and
give you a back massage, maybe.
