ES6 module syntax

[scarlac]

It'd be great if we could get ES6 module syntax working, so it'd be possible to import this package using:

import { init as initDebugger } from 'electron-debug';

Which doesn't seem possible at the moment because the initialization function is exported via module.exports = function() { ... } and not as any named export.

The best solution would obviously be to import initDebugger from 'electron-debug' but that would break backwards compatibility which I assume we wouldn't want.

The change seems like something that could be made fairly quickly, so let me know if prefer me to submit a PR.

(For completeness, if you try import foo from 'electron-debug'; foo({}) then Webpack will throw a warning.)