To install dependencies(node_module) from package.json, run:

  $ npm install

To include the React router:

  $ npm install react-router@2.0.0 --save

What does the router do for single page apps?

  "You need to ensure that navigating within your app adjusts the URL appropriately. You need to ensure your browser's history is properly synchronized with each navigation to allow users to use the back and forward buttons. If users bookmark a particular view or copy/paste a URL to access later, you need to ensure that your single-page app takes the user to the correct place.

  To deal with all of this, you have a bucket full of techniques commonly known as routing."