title: rowHasChanged Undefined is not a constructor
body: <p>Hello I'm creating a grid and I have this constructor in my class</p>
  
  <pre><code>export class Grid extends Component {
      constructor (props) {
          super(props)
          var ds = new ListView.Datasource({rowHasChanged: (r1, r2) =&gt; r1 !== r2})
          this.state = {dataSource: ds.cloneWithRows(this._genRows({}))}
      }
  .
  .
  .
  }
  </code></pre>
  
  <p>I'm getting the following error when I try to run this: </p>
  
  <blockquote>
    <p>Undefined is not a constructor (evaluating 'new)
    _reactNative.ListView.Datasource({rowHasChanged:function rowHasChanged(r1,r2){returnr1!==r2;}})')</p>
  </blockquote>
  
  <p>Can someone give me a hand on this? 
  Thank you in advance!</p>