change function declaration; simplify CSS selectors
change function declaration; simplify CSS selectors

raneku/chessboardjs,blipjoy/chessboardjs,ThiagoGarciaAlves/chessboardjs,ThiagoGarciaAlves/chessboardjs,raneku/chessboardjs,mauronunez/chessboardjs,ngocdaothanh/chessboardjs,ngocdaothanh/chessboardjs,mattyhead/chessboardjs,mattyhead/chessboardjs,mauronunez/chessboardjs,oakmac/chessboardjs,blipjoy/chessboardjs,raneku/chessboardjs,blipjoy/chessboardjs