old_contents: import Router from 'ampersand-router'
  import React from 'react'
  import HomePage from './pages/home'
  import ContactPage from './pages/contact'
  import Layout from './layout'
  
  export default Router.extend({
    renderPage (page, opts = {layout: true}) {
      if (opts.layout) {
        page = (
          <Layout>
            {page}
          </Layout>
        )
      }
      React.render(page, document.body)
    },
  
    routes: {
      '': 'home',
      'contact': 'contact'
    },
  
    home () {
      this.renderPage(<HomePage/>)
    },
  
    contact () {
      this.renderPage(<ContactPage/>)
    }
  })
  
new_contents: import Router from 'ampersand-router'
  import React from 'react'
  import HomePage from './pages/home'
  import ContactPage from './pages/contact'
  import NotFoundPage from './pages/not-found'
  import Layout from './layout'
  
  export default Router.extend({
    renderPage (page, opts = {layout: true}) {
      if (opts.layout) {
        page = (
          <Layout>
            {page}
          </Layout>
        )
      }
      React.render(page, document.body)
    },
  
    routes: {
      '': 'home',
      'contact': 'contact',
      '*notFound': 'notFound'
    },
  
    home () {
      this.renderPage(<HomePage/>)
    },
  
    contact () {
      this.renderPage(<ContactPage/>)
    },
  
    notFound () {
      this.renderPage(<NotFoundPage/>)
    }
  })
  
subject: add not-found page to router