Button icon is not dynamic

[mischkl]

I'm submitting a ... (check one with "x")

[x] bug report => search github for a similar issue or PR before submitting
[ ] feature request
[ ] support request => Please do not submit support request here, instead see http://forum.primefaces.org/viewforum.php?f=35

Current behavior
If a button's icon is bound to a field in the parent component and that field changes, it does not react to the change.

Expected behavior
If the field changes the icon should also change.

Minimal reproduction of the problem with instructions

@Component({
  selector: 'my-component',
  template: '<button pButton [icon]="myIcon" (click)="onClick()"></button>'
})
export class MyComponent {
  myIcon: string = 'fa-bell';

  onClick() {
    this.myIcon = 'fa-bell-o';
  }
}

Icon should change, but doesn't.

What is the motivation / use case for changing the behavior?
In my case it is a toggle button that should change the icon based on the state of the toggle.

Please tell us about your environment:
Windows 7, Node 6.9.1

• Angular version: 2.1.0

• PrimeNG version: 1.0.0

• Browser: all

• Language: TypeScript