support for older browsers (ie9, ie8)

[lauterburgp]

hi there

thank you so much for this great plugin!

i discovered however that your plugin isn't quite compatible with ie9. The calculation of hours is somehow not the same as in other browsers. it is quote obvious, even in the provided demo. are there any plans on your side to making it compatible with ie9 or even ie8? because there's still a considerable amout of people stuck with these versions ... sadly

best regards
patrick