Bump React in development (#2122)

Author: gaearon

packages/react-scripts/package.json

@@ -61,8 +61,8 @@
     "whatwg-fetch": "2.0.3"
   },
   "devDependencies": {
-    "react": "^15.3.0",
-    "react-dom": "^15.3.0"
+    "react": "^15.5.4",
+    "react-dom": "^15.5.4"
   },
   "optionalDependencies": {
     "fsevents": "1.0.17"