title: select2 event fires twice in angular4
body: <p><strong>Markup</strong></p>
  
  <pre><code>&lt;select2 
           [data]="data"
           [width]="1024"
           [options]="options"
           [value]="selectedData"
           (valueChanged)="onTagChanged($event)"&gt;
  &lt;/select2&gt;
  </code></pre>
  
  <p><strong>Angular 4 Component</strong></p>
  
  <pre><code>onTagChanged(data: { value: string[] }): void {
      console.log(data);
      this.selectedData = data.value;
  }
  </code></pre>
  
  <blockquote>
    <p>event <code>valueChanged</code> fires twice, how can prevent it.</p>
  </blockquote>