openxlsx development version

include tests for cloneWorksheet

openxlsx 4.1.4

Use zip::zipr() instead of zip::zip().
Keep correct visibility option for loadWorkbook. #12
Added getCellRefs as function. #7
update to rogygen2 7.0.0
Added parameter for customizing na.strings
Add space surrounding "wrapText" #17
Corrected Percentage, Accounting, Comma, Currency class on column level

openxlsx 4.1.3

Added a NEWS.md file to track changes to the package.