Use Just to automate running tests and linters locally

[simonw]

I keep committing code that fails additional tests like mypy and flake8 and black. Automate those using Just.

[simonw]

just now defaults to running the tests and linters.

just test runs the tests - it can take arguments, e.g. just test -k transform

just lint runs all of the linters.

just black applies Black.

In all case it assumes you are using pipenv, at least for the moment.

[simonw]

just -l now does this:

% just -l
Available recipes:
    black         # Apply Black
    cog           # Rebuild docs with cog
    default       # Run tests and linters
    lint          # Run linters: black, flake8, mypy, cog
    test *options # Run pytest with supplied options