The \Pchess\Chess\Piece class is a simple value object representing a piece in \Pchess\Chess\Chess.
The object is composed of a $type and a $color (both are a single-character string).
The type can be "k", "q", "r", "b", "n", or "p" (respectively King, Queen, Rook, Bishop, Knight, or Pawn).
The color can be "b" (black) or "w" (white).
The string representation is piece type, in uppercase when white and in lowercase when black. For example, "B" is a white Bishop, while "q" is a black Queen.