- add three tokenizers ([fugashi-ipadic](https://github.com/polm/fugashi), [fugashi-unidic](https://github.com/polm/fugashi), [tinysegmenter](https://github.com/SamuraiT/tinysegmenter)) to toiro
- add additional_tokenizers to compare
tokenizers.compare(filename, additional_tokenizers)
- add [sample codes](https://github.com/taishi-i/toiro/blob/develop/PyConJP2020/PyConJP2020_Online.ipynb) and [slides](https://speakerdeck.com/taishii/pycon-jp-2020) in [PyCon JP 2020](https://pycon.jp/2020/)
- add python-package.yml to .github/workflows
- fix toiro.\__version\__