modernize

- update react
- get rid of componentWillReceiveProps
- add service worker and fix pwa issues

src/index.js

@@ -3,9 +3,9 @@ import ReactDOM from 'react-dom';
 import './index.css';
 import App from './App';
 //import {elevate} from './infrastructure/elevator';
-//import registerServiceWorker from './registerServiceWorker';
+import registerServiceWorker from './registerServiceWorker';
 
 //elevate();
 
 ReactDOM.render(<App />, document.getElementById('root'));
-//registerServiceWorker();
+registerServiceWorker();