- very basic XLSX / XLSM write support with roundtrip tests (XLSB stubs)
- reorganized source tree
- new XLSB range check ensures that A1 is not emitted for empty sheets
- SSF table emitted in output (consistent with js-xls)
- CLI supports writing

Backwards-incompatible changes:
o new Property aliases (see CORE_PROPS and EXT_PROPS)
o FILETIME custom properties parsed as JS Dates
o `xlsx2csv` -> `xlsx` (and `bin/xlsx{2csv,}.njs`)

- read and readFile accept opts argument:
o cellNF (default false) true -> cell.z holds number format string
o sheetStubs (default true) false -> stub cells not emitted

- name consistency (parse_workbook -> parse_wb_xml)
- README updates
- CONTRIBUTING notes added