- `--help`
- installation procedure
- extract space, title, and/or page ID from pandoc yaml header

Nice to have, but unlikely to be implemented:

- optional table of contents
- more than just markdown (restructured text, html, etc)
- configurable banner at the top of rendered pages ("this uploaded from...")
- color output, one line per file
- detecting and uploading included image files as attachments.
  `confluence-sync` does this