title: Angular 2 tree only shows root nodes
body: <p>The angular2-tree library has a straightforward <a href="https://angular2-tree.readme.io/docs#basic-usage" rel="nofollow noreferrer"><em>Basic Usage</em> example</a>.  However, when I put it into my project, only the root nodes are rendered.  In other words, the tree should have parents (rootA, rootB) and children, </p>
  
  <pre><code>export class App {
    nodes = [
      {
        id: 1,
        name: 'rootA',
        children: [
          { id: 2, name: 'child1' },
          { id: 3, name: 'child2' }
        ]
      },
      {
        id: 4,
        name: 'rootB',
        children: [
          { id: 5, name: 'child2.1' },
          {
            id: 6,
            name: 'child2.2',
            children: [
              { id: 7, name: 'subsub' }
            ]
          }
        ]
      }
    ];
  </code></pre>
  
  <p>But all I see are root nodes.  </p>
  
  <p>There are no compilation issues, and I've included the css import:</p>
  
  <pre><code>@import '~angular-tree-component/dist/angular-tree-component.css';
  </code></pre>
  
  <p>Has anyone had a similar issue?</p>
  
  <p><a href="https://i.stack.imgur.com/drNKm.png" rel="nofollow noreferrer"><img src="https://i.stack.imgur.com/drNKm.png" alt="enter image description here"></a></p>
  
  <p>Stack is Angular 4, Chrome, Windows 10.</p>