Fix tests + fix lint issues + apply consistent formatting with Black + Dockerise

[daaain]

Description of change

I wanted to implement a new feature, but couldn't run the tests properly (as right now they need an unspecified Postgres setup to be done beforehand) so ended up creating a reproducible setup with Docker. While doing it I also applied consistent formatting using Black, which then made it possible to lint it with Flake8.

With these changes linting the code and running the whole test suite is as simple as make docker-ci with the only dependency being Docker, ie you don't even have to have Postgres running on your machine.

I appreciate that this PR is huge so no offense if you don't want it, but I thought I should at least offer it.

Actually realised a couple of smaller changes from our fork snuck in too, namely using psycopg2-binary and handling geo features with shapely.

QA steps

• automated tests passing
• manual qa steps passing (list below)

Risks

Rollback steps

• revert this branch

[cmerrick]

Hi @daaain, thanks for your contribution!

In order for us to evaluate and accept your PR, we ask that you sign a contribution license agreement. It's all electronic and will take just minutes.

[cmerrick]

You did it @daaain!

Thank you for signing the Singer Contribution License Agreement.