Fix merging default options and add header_div option
Fix merging default options and add header_div option

sdbeng/simple_calendar,rodrigoargumedo/simple_calendar,sdbeng/simple_calendar,timshingyu/simple_calendar,TuxmAL/simple_calendar,excid3/simple_calendar,rodrigoargumedo/simple_calendar,timshingyu/simple_calendar,sdbeng/simple_calendar,rodrigoargumedo/simple_calendar,TuxmAL/simple_calendar,timshingyu/simple_calendar,excid3/simple_calendar,excid3/simple_calendar