Checkbox: Indeterminate property should be updated after user interaction

Messing around with the `indeterminate` property on a checkbox, the binding doesn't seem to update when the user clicks the checkbox itself.

http://jsfiddle.net/6Evrq/263/

I would expect after checking the checkbox that `indeterminate` would return to false.

I would also expect that setting `indeterminate` to true afterwards would properly reflect in the checkbox. (but since it already is true, it doesn't apply its setting)