Merge pull request #1 from oyamad/kusano

Thanks.
Minor changes, to comply with PEP8
*.ipynb_checkpoints/ added to .gitignore
br_correspondence modified
br_correspondence: exact equality replaced with np.isclose to allow a tolerance
Added a test of br_correspondence for a case with two opponents
Merge pull request #2 from oyamad/develop

Develop
Extended br_correspondence to N players version.