title: ES6 '...' notation gives error in jslint?
body: <p>I get <code>Unexpected token</code> error whenever I run the code against jslint while using '...' notation. I am using grommet-toolbox for Grommet UI (and UI/UX framework for React) and so when I run <code>gulp dev</code> command I get this error, thereby not being able write code like below:</p>
  
  <p><code>return {...state, fetching: true}</code></p>
  
  <p>(The above code is in line 10 of this file: <a href="https://github.com/learncodeacademy/react-js-tutorials/blob/master/5-redux-react/src/js/reducers/tweetsReducer.js" rel="nofollow">https://github.com/learncodeacademy/react-js-tutorials/blob/master/5-redux-react/src/js/reducers/tweetsReducer.js</a>)</p>
  
  <p>How to resolve this issue?</p>