Refactor Menu specs
Refactor Player, Menu, and Runner specs to avoid stubbing system under test
Rename Stringifier to Strings; create new IOInterface class, leaving only pure-IO in IO class; ensure no specs stub the system under test
Make some Menu methods private and refactor tests to reflect this
Add History class and specs
Restructure Runner to record elements of game history as they are created
Add PGWrapper class and specs
Modify Runner specs to finish rebase with master