CI and local dev improvements

[ ] Switch to github actions (current setup is not working at all due to travis website change)
[ ] Fail build if linting fails
[ ] Use pydocstyle, black --check, isort --check, and maybe mypy for linting
[ ] Add Makefile for linting/testing/formatting (with black and isort) and for installing dev dependencies
[ ] Stop using imp (pytest gives warning)
[ ] Add makefile with test and lint commands
[ ] Use poetry for managing dev dependencies and to publish to pypi?

noctuid / zscroll