Mantichora

Changes from the previous release: ([diff](https://github.com/alphatwirl/mantichora/compare/v0.11.0...v0.12.0))
- addressed the issue [5](https://github.com/alphatwirl/mantichora/issues/5)
- added tests on Windows and macOS in GitHub Actions

Changes from the previous release: ([diff](https://github.com/alphatwirl/mantichora/compare/v0.10.0...v0.11.0))
- updated `.coveragerc`, `README.md`
- moved the dependency list from `requirements` to `setup.py`
- removed `TaskPackage`, replaced with `functools.partial`
- moved from Travis CI to GitHub Actions
- added test on Python 3.9 in GitHub Actions
- changed the default branch to "main"

Changes from the previous release: ([diff](https://github.com/alphatwirl/mantichora/compare/v0.9.9...v0.10.0))
- added `threading` mode, which can be selected by new option `mode`
- added brief sleeps in "while" loops, which improves performance in some circumstances
- removed code for Python 2.7

Changes from the previous release: ([diff](https://github.com/alphatwirl/mantichora/compare/v0.9.8...v0.9.9))
- added option `mp_start_method`
- users can choose the [start method](https://docs.python.org/3/library/multiprocessing.html#contexts-and-start-methods) of `multiprocessing` from three options: `fork`, `spawn`, and `forkserver`
- addressing the issue 4 comment [599216616](https://github.com/alphatwirl/mantichora/issues/4#issuecomment-599216616)

Changes from the previous release: ([diff](https://github.com/alphatwirl/mantichora/compare/v0.9.7...v0.9.8))
- stopped supporting Python 2.7
- updated to use the "fork" multiprocessing start method, addressing the issue [4](https://github.com/alphatwirl/mantichora/issues/4)

Changes from the previous release: ([diff](https://github.com/alphatwirl/mantichora/compare/v0.9.6...v0.9.7))
- added tests on Python 3.8 in Travis CI