Remove log() function
Add accessor fn's to piece.js; refactor rook.js
Remove two unused methods pieceValid() & pawnValid()
Change local variable from 'Piece' to 'Square'
Add methods grid, square, piece, accessible
Add functions samePosition() & anyAcross()
Add method accessible()
Add method piece()
Create mediator.js
Move responsibility for king safety from board.js to king.js
Move responsibility for king safety from board.js to king.js
Provide access to a mediator for board and all pieces
Test use of mediator
Allow publish() to use variable arguments
Allow mediator to return values
Validate king movement by using mediator
Merge branch '24-11-differentiate-piece-classes'