title: Duplicate parent paths in url bar
body: <p>Using:</p>
  
  <pre><code>"react-router": "^2.0.0",
  "react-router-relay": "^0.9.0",
  </code></pre>
  
  <p>When I push any link under a parent path, the parent path is duplicated in the URL bar once for every new <code>router.push</code> call.</p>
  
  <pre><code>// http://localhost:3000
  
  router.push('auth/profile')
  // http://localhost:3000/auth/profile
  
  router.push('auth/profile')
  // http://localhost:3000/auth/auth/profile
  
  router.push('auth/browse')
  // http://localhost:3000/auth/auth/auth/browse
  </code></pre>
  
  <p>When I log the <code>location</code> (from <code>react-router</code>), it does not show the duplicates. Maybe the browser is pushing the parent path onto the basename?</p>