title: Default router: make id persist to all children
body: <p>I want to have an <code>id</code> to persist through all routes.</p>
  
  <p>e.g. <code>www.website.com/#/:id/routes</code></p>
  
  <p>I have tried to do the following:</p>
  
  <pre><code>export default new Router({
      routes: [
          {
              path: '/:id/',
              props: true,
              component: FirstView,
              children: [
                  {
                      path: '/',
                      name: 'Second',
                      component: SecondView
                  }
              ]
          }
      ]
  });
  </code></pre>
  
  <p>but i cant get the <code>:id</code> to persist. Any ideas?</p>