Make insignificant changes.
Amend the fn #kingside? so that a second position param is
no longer needed.
Fix small error.
Refactor the name of the constant 'unset-passant-pos'.
Change filtering function to _.true:
I assume that later filtering by positional equivalence is faster than
filtering by the color of a position's chessman.
Refactor the fn #modifyCastlingRights.
Refactor the fns #get-potential-castling-moves and
#modifyCastlingRights.
Amend a constant name.
Amend a constant name.
Add knight-spec.js and rook-spec.js to spec files.
Add specs for the 'knight' chessman type.
Add specs for the 'rook' chessman type.