fix tests for IE11
fix tests for IE11

oleg-babintsev/fullcalendar,arshaw/fullcalendar,fullcalendar/fullcalendar,arshaw/fullcalendar,oleg-babintsev/fullcalendar,fullcalendar/fullcalendar,arshaw/fullcalendar,oleg-babintsev/fullcalendar,fullcalendar/fullcalendar,fullcalendar/fullcalendar,arshaw/fullcalendar