Merge pull request #75 from johmue/master

support for new methods of libxl 3.6.0
Added extra validation
Adjust test
Updated change log
added check if tested methods are available
added ExcelSheet::rowHidden(), ExcelSheet::colHidden(), ExcelSheet::setRowHidden() and ExcelSheet::setColHidden()
Merge remote-tracking branch 'upstream/master'
updated changelog