#619 : val takes an optional argument to avoid triggering 'change'

This is a suggested fix for this issue #619 

I simply added an optional 'triggerChange' argument to the two "val" functions, and used it to avoid triggering (as demonstrated by the test-619.html file). 

Although, I'm not sure where to document it, nor if the setVal function should also be changed. 

Hoping this helps. 

Thanks
PH