Change file name to 'fn-chess-4'.
Add a mixin for #basicMove and #modifyCastlingRights.
Modify the parameter-structure requirements for
the api functions.
Adapt the specs to the new parameter structure of the
api functions.
Refactor files: remove unused functions.
Removes specs for nonexistent functions.
Refactor function names.
Make pawn #move API consistent with that of other types.
Re-add game-services specs to spec list.
Update pawn specs for new pawn #move API.
Amend parameter structure of game-service functions so
that they are compatible with the API of the chessman types.
Add fn #checkmate?.
Add specs for #checkmate?; do minor reformatting.
Remove mydash dependency.