Fix incorrect plot mode in react example (#1559)

Author: gricey432

_posts/plotly_js/fundamentals/react/2018-01-16-quick_start.html

@@ -22,7 +22,7 @@
             x: [1, 2, 3],
             y: [2, 6, 3],
             type: 'scatter',
-            mode: 'lines+points',
+            mode: 'lines+markers',
             marker: {color: 'red'},
           },
           {type: 'bar', x: [1, 2, 3], y: [2, 5, 3]},