title: Disabled button is still clickable in angular material
body: <pre><code>&lt;a  md-icon-button [routerLink]="['./new']" queryParamsHandling="merge"
                  mdTooltip="Add Document" [disabled]="isAddButtonDisabled(selectedAssociation)"&gt;
                  &lt;md-icon&gt;add&lt;/md-icon&gt;
              &lt;/a&gt;
  </code></pre>
  
  <p>The button is firing click event even when the button is disabled. Is there a way to prevent the click?</p>