Respect NODE_PATH environment variable

Created by: tp

I wanted to try out create-react-app on our internal monorepo, which is basically structured into 2 folders: "apps" and "components".

The "apps" contain just an entry index.js file and their build/transpile configuration and import a root component from the components directory.

This is currently solved by directing imports using NODE_PATH environment variable to make tools look into the components folder (so that you can write import Button from 'ns-button' instead of import Button from '../../../components/ns-button).

Personally I would feel that this would be worthwhile to support so this project could work with a wide variety of "non-standard" project layouts.