title: Vue nested routing does not including dynamic parameters
body: <p>I have two routes, say posts &amp; pages, inside each user route, like 
  <code>/user/foo/pages</code>, <code>user/foo/posts</code>, <code>/user/bar/pages</code>, <code>user/bar/posts</code>
  where <code>foo</code> and <code>bar</code> are the dynamic content. However nested routing in vue does not including those <code>foo</code> and <code>bar</code></p>
  
  <p>router.js</p>
  
  <pre><code>export default new Router({
    routes: [
      {
        path: '/user/:id',
        name: 'user',
        component: User,
        children: [
          {path: 'posts', name: 'posts', component: Posts},
          {path: 'pages', name: 'pages', component: Pages},
        ]
      }
    ]
  })
  </code></pre>
  
  <p>User.vue</p>
  
  <pre><code>&lt;router-link to="posts"&gt;Posts&lt;/router-link&gt;
  &lt;router-link to="pages"&gt;Pages&lt;/router-link&gt;
  </code></pre>
  
  <p>The result vue is producing when i am already inside <code>foo</code> or <code>bar</code>, is</p>
  
  <pre><code>&lt;a href="#/user/posts"&gt;Posts&lt;/a&gt;
  &lt;a href="#/user/posts"&gt;Pages&lt;/a&gt;
  </code></pre>
  
  <p>However the expected result should be (when i am inside <code>foo</code>)</p>
  
  <pre><code>&lt;a href="#/user/foo/posts"&gt;Posts&lt;/a&gt;
  &lt;a href="#/user/foo/pages"&gt;Pages&lt;/a&gt;
  </code></pre>