0.1.9

Lots of changes in this release; the bulk of the work/improvements were around improving the docx backend; it's nearly ready to escape its feature flag (will that be the 0.2.0 release? Maybe!). Also includes more appropriate error handling throughout.

This release (also) includes:

• Majority feature coverage for docx backends, including (limited) support for lists, tables, block images, a better standard stylesheet, etc.,
• Character substitutions, mirroring what asciidoctor does, more or less.
• Limited (but OK coverage) of character entities replaced back to their font-character in docx builds
• Generally much better error handling; scanning, parsing, and backends now all return Result<>s, although there's an argument to be made that the render_ functions should return actual Errors instead of relying on Anyhow, but that's something I'm still thinking about.
• Misc., bug fixes to parsing/scanning

Still no binaries with this release (that feels like a 1.2 thing, when I actually want to start sharing around the docx capabilities), so please still install via cargo, or clone the repo directly.