Add example for backtracking when a blur event sets a className bound property

[jayjayjpg]

In this example backtracking re-rendering seems to occur once a property is set on an input element whose disabled state is mutated which in turn triggers a blur event.

If this blur event happens to mutate a property that is bound through classNameBindings the assertion will be thrown.

[GavinJoyce]

Thanks @jessica-jordan