Created by: Timer
This removes the ie 9 target and forceAllTransforms since we're dropping IE9 support by default.
We want to allow target browsers to be configurable via the browserslist key in package.json.
This also enables useBuiltIns for smaller bundles.
I've also adjusted the defaults we generate for a more ergonomic development experience.
There's still no story for users upgrading from * -> 2.x (it'd use browserlist defaults currently).