Change server dev setup

- `npm start` only starts the applications and requires that `npm run
   build` is already run
 - `npm run dev-server` runs the build and starts the server with
   nodemon
 - update README

README.md

@@ -4,12 +4,32 @@
 
 ## Getting started
 
+Clone this repository and install dependencies:
+
     yarn
 
 ## Development
 
+To develop the application and to see changes live, start the frontend
+development server:
+
     npm run dev
 
-## Server
+## Development Server
 
+To develop the server setup, run:
+
+    npm run dev-server
+
+This runs the frontend production build and starts the Express.js
+server in `server/index.js` that renders the application routes in the
+server. The server is automatically restarted when there are changes
+in the `server/` directory.
+
+Not that this server does **not** pick up changes in the frontend
+application code.
+
+## Production Server
+
+    npm run build
     npm start

package.json

@@ -19,6 +19,7 @@
     "build": "react-scripts build",
     "test": "react-scripts test --env=jsdom",
     "eject": "react-scripts eject",
-    "start": "npm run build&&node server/index.js"
+    "start": "node server/index.js",
+    "dev-server": "npm run build&&nodemon --watch server server/index.js"
   }
 }