title: Have parent state default to child state using ui-router
body: <p>I have this state structure:</p>
  
  <pre><code>.state('places',
  {
      url:'/places',
      controller:'PlacesController',
      templateUrl:'views/places.html'
  })
  .state('places.city',
  {
      url:'/:city',
      templateUrl:function(stateParams)
      {
          return 'views/places/'+stateParams.city+'.html';
      }
  });
  </code></pre>
  
  <p>It works nicely except when the URL is simply <code>/places</code> without a city after it.<br>
  How can I have a default value for <code>templateUrl</code> in the child state?</p>
  
  <p>I'm thinking the best way would be to set the ui-view from <code>PlacesController</code>, however that doesn't seem to be possible.</p>