Merge pull request #1 from erebos42/staging

Fix json by opening files not in binary mode.
Merge pull request #1 from erebos42/staging

Fix json by opening files not in binary mode.
Merge branch 'master' of https://github.com/wichmann/yatts
Implemented adding and removing of player
Added __str__ methods and test for data classes
Made gui.py executable + some minor stuff
Fix saving of matches to file