docs(readme): add Greenkeeper badge

README.md

@@ -1,5 +1,7 @@
 # create-react-app with a Node server on Heroku
 
+[![Greenkeeper badge](https://badges.greenkeeper.io/mars/heroku-cra-node.svg)](https://greenkeeper.io/)
+
 A minimal example of using a Node backend (server for API, proxy, & routing) with a [React frontend](https://github.com/facebookincubator/create-react-app).
 
 To deploy a frontend-only React app, use the static-site optimized  

greenkeeper.json

@@ -0,0 +1,10 @@
+{
+  "groups": {
+    "default": {
+      "packages": [
+        "package.json",
+        "react-ui/package.json"
+      ]
+    }
+  }
+}