Datasette 0.19: plugin preview (with release notes)

Releasing v0.18 - support for units!

Refs simonw#203

Release 0.17 to fix issues with PyPI

See https://twitter.com/simonw/status/984862976447414272

Releasing v0.16

Releasing v0.15

Releasing v0.14

Release version 0.13

Changelog for 0.12 release

Version 0.11

Version 0.10