title: Nativescript ListView showing only one item
body: <p>I ma following a course on pluralsight and I have encountered an odd problem.
  My list view is only showing the first element and nothing else.
  This is odd and i've used list views without problem before so I'm not sure where the error is coming from.</p>
  
  <p>Layout: </p>
  
  <pre><code>    &lt;Page xmlns="http://schemas.nativescript.org/tns.xsd"
   loaded="pageLoaded"&gt;
    &lt;GridLayout rows="auto, *"&gt;
      &lt;!-- Header --&gt;
      &lt;StackLayout cssClass="page-header"&gt;
        &lt;Label text="Header" cssClass="page-title bold" horizontalAlignment="center" margin="15"/&gt;
      &lt;/StackLayout&gt;
  
      &lt;!-- Sessions Views --&gt;
      &lt;GridLayout rows="auto, *" row="1"&gt; 
  
        &lt;ListView items="{{ sessions }}"&gt;
          &lt;ListView.itemTemplate&gt;
            &lt;Label text="{{ title }}"/&gt;
          &lt;/ListView.itemTemplate&gt;
        &lt;/ListView&gt;
  
      &lt;/GridLayout&gt;
    &lt;/GridLayout&gt;
  &lt;/Page&gt;
  </code></pre>
  
  <p>Typescript:</p>
  
  <pre><code>import { EventData, Observable } from "data/observable";
  import { Page } from "ui/page";
  
  var page: Page;
  var tempSessions = [
      {
          id: '0',
          title: "Stuff"
      },
      {
          id: '1',
          title: "Stuffly"
      },
      {
          id: '2',
          title: "Stufferrs"
      },
      {
          id: '3',
          title: "Event 4"
      }
  ];
  export function pageLoaded(args: EventData){
      console.log(JSON.stringify(tempSessions));
      page = &lt;Page&gt;args.object;
      page.bindingContext = new Observable({
          sessions: tempSessions
      });
  }
  </code></pre>
  
  <p>I suspected that the first list item was completely filling the gridLayout however placing a border around it reveals that it is not.</p>