SelectedOptions binding not updating non-observable properties

When you bind to a non-observable javascript property with the "selectedOptions" binding the value of the property is not updating when you change selection. As opposed to binding with a "value" binding.

Look at this JsFiddle http://jsfiddle.net/angelyordanov/6MCzp/.
1) Click the "check" button to see what's the current model state.
2) Change the selection in both selects.
3) Click again the button to see that just the "value" is correctly updated.

This is a minor issue. And the fix is even minor. I tracked the offending line back to the initial commit so i'm not sure if its actually a bug.

I've updated the specs too.