Validate against the viewValue instead of the modelValue for ui-validate-watch

## Replicate Issue:
goto [Validate demo page](http://angular-ui.github.io/ui-utils/#/validate)
enter 'small' into first password box
enter 'smaller' into second password box
You will see 'Passwords do not match!'
change the first password box to 'smaller'

The now valid inputs wont be reflected as valid until the second password box is changed as the model value of the second input is undefined until the second input has a valid value.

## The Fix
Change the ui-validate-watch implementation to send the $viewValue to the validate function instead of the $modelValue

I have added a test case that will fail unless the $viewValue is used