Created by: kasperpeulen
follow up on https://github.com/facebookincubator/create-react-app/pull/2358
Autoprefixer's browsers option is currently hardcoded. This PR adds the browserslist key in package.json which allows developers to set different browsers for both production and development. Autoprefixer which relies on Browserslist will find its config automatically. This PR fixes #2248 (closed) and #892 (closed)