use key instead of ref for unique key for components in loop

src/containers/Home.js

@@ -23,7 +23,7 @@ class Home extends React.Component {
         <div>
           { this.props.loading && 'Loading...'}
           { this.props.videos.map(video => {
-            return (<div ref={ video.id }>{ video.title }</div>);
+            return (<div key={ video.id }>{ video.title }</div>);
           })}
         </div>
       </div>