support query by featured artwork or artist
cleanup
tests
docs
better docs
Merge pull request #89 from craigspaeth/byfeatured

@dzucconi: Query articles by artist or artwork it's featured to
better
Merge pull request #90 from craigspaeth/byfeatured

@craigspaeth: Hoist db references & clear error message
ensure thumbnails
cleanup
Merge pull request #91 from craigspaeth/migrations

@craigspaeth: Ensure thumbnails in migration