This license achieves everything that dual-licensing under MIT + Apache
aims for, but without the weirdness of being under two licenses.
Having checked external contributions, I feel pretty confident that I
can unilaterally make this license change, as people have only
contributed a handful of one-line changes of no significance towards
copyrighted work up to this point.
This introduces a new `--start-at` CLI argument and corresponding
`start_at()` method on the Exporter type that allows exporting of only a
given subdirectory within a vault.
See the updated README file for more details on when and how this may be
used.
This removes mdBook in favor of a flat docs folder generating a single
`README.md` in the repository root.
Installation and usage instructions have also been expanded slightly.
