Added notation parsing for pawns.
Working on tests.
Moved files around. added more tests.
Promotion is working.
Wrote a bunch of rules and notation tests.
Wrote more tests. did more peice -> piece.
Bishop and knight tests.
Wrote find_sliding_piece function.
Fixed en passant and pawns moving through others on double move.
wrote tests that checks that stale castles are not allowed.
weird state with inifinte loop. probably dont want this.
All tests seem to be passing.