old_contents: import React from 'react';
  import { App } from './App';
  import '../static/style.css';
  
  React.render(<App />, document.getElementById('root'));
  
new_contents: import React from 'react';
  import Router from 'react-router';
  import '../static/style.css';
  import routes from './routes';
  
  Router.run(routes, Router.HistoryLocation, (Handler) => {
    React.render(<Handler />, document.getElementById('root'));
  });
subject: add routing to entry point js file