title: Not recommended to use "use strict" in ES6?
body: <p>I'm not familiar with ECMAScript 6 yet. I've just cloned the React Starter Kit repo, which uses ES6 for application code. I was surprised to see that the linter is <a href="https://github.com/kriasoft/react-starter-kit/blob/master/.eslintrc" rel="noreferrer">configured</a> to forbid occurences of the <code>use strict</code> directive, which I thought was recommended in pre-ES6 JavaScript. So what's the point?</p>