Remove the Makefile since it is not needed any more

Makefile

-upload: clean
-	@[ "$$(git symbolic-ref -q HEAD)" == "refs/heads/master" ] || \
-		{ echo "Uploading can only be done on the master branch."; exit 1; }
-	python setup.py sdist && \
-	python setup.py bdist_wheel --universal && \
-	twine upload dist/*
-
-clean:
-	rm -rf build dist *.egg-info
-
-.PHONY: clean upload