Document `POSTGRES_EXTRA_ANNOTATE_SQL`

Gracefully handle the primary key already being included in the parti…

…oning key

Merge pull request SectorLabs#179 from SectorLabs/181799346-postgis-c…

…ompatibility

Support both psqlextra and PostGis backends at the same time

Merge pull request SectorLabs#176 from SectorLabs/181799346-args-fix

Fix arguments for an as_sql wrapper

Merge pull request SectorLabs#174 from SectorLabs/181799346-caller-sq…

…l-comment

Append the caller data to each SQL query

Fix failing snapshot test for pgpartition

Add support for `IN (VALUES (a), (b), (c))` lookups

This is a bit experimental so I am not adding any documentation yet.

Let CircleCI publish the package to PyPi

Bump version number to 2.0.4rc2