Use React 16 in development

Author: gaearon

packages/react-scripts/package.json

@@ -58,8 +58,8 @@
     "whatwg-fetch": "2.0.3"
   },
   "devDependencies": {
-    "react": "^15.5.4",
-    "react-dom": "^15.5.4"
+    "react": "^16.0.0",
+    "react-dom": "^16.0.0"
   },
   "optionalDependencies": {
     "fsevents": "1.1.2"