Make react-dev-utils/webpackHotDevClient work with webpack 2

Created by: michalkvasnicak

I am working on a tool similar to create-react-app but plugin based with webpack 2 support. I want to use react-dev-utils as a dependency because I need webpackHotDevClient but it's not compatible with webpack 2.

Fix is simple so I am asking if someone is working on this or should I create a PR?