Switch to new, maintained fork of bumpversion

Author: gahjelle

pyproject.toml

@@ -38,6 +38,6 @@ requires           = [
 
 
 [tool.flit.metadata.requires-extra]
-dev                = ["black", "bumpversion", "flake8", "flit", "mypy"]
+dev                = ["black", "bump2version", "flake8", "flit", "mypy"]
 test               = ["pytest", "pytest-cov", "tox"]