Move init code from MatchStatusPersistence.get_from_file
Replace match_data JSON file w/ PStore

I was encountering test failures where the match_data file was blank.
This is because I had overlooked the fact that file access doesn't lock
by itself. In my search for alternatives, I came across this article:

https://robm.me.uk/ruby/2014/01/25/pstore.html

PStore is the way to go for this application.
Replace BET_FILE with PStore