Merge pull request #13 from stac-api-extensions/pv/release-1.0.0

release prep for 1.0.0

Merge pull request #7 from stac-api-extensions/pv/1.0.0-rc.3

pre for 1.0.0-rc.3 release

Merge pull request #3 from stac-api-extensions/pv/release-1.0.0-rc.2

updates for release 1.0.0-rc.2