version bump 0.6.17: XLS features

- updated SSF to 0.6.4
- FILETIME parsing
- codepage handling (h/t @xch89820)
- coverage test spinner (to prevent travis timeouts)
- XLS adjust range if outside of Dimensions (h/t @euskode)
- hyperlink support (mirroring js-xlsx, h/t @sysarchitect)