Fix factual error on date formats, typos, and erroneous links.

### Changed
- Update year to match in every README example.
- Reluctantly stop making fun of Brits only, since most of the world
  writes dates in a strange way.

### Fixed
- Fix typos in recent README changes.
- Update outdated unreleased diff link.

Acknowledge GNU change log style, point to ISO 8601, clean links.

README section on 'yanked' releases.

Markdown links to tags on versions headings.

Remove empty sub-section headers, use "change log" instead of "CHANGE…

…LOG" when not referring to the file itself.

Added "Why should I care?" section in README.

Explain reverse chronological date ordering.

Create initial CHANGELOG example.