Reimplement Jump.hdl using Mux8Way.hdl.

books/nand2tetris/projects/5_computer_architecture/Jump.hdl
	-The `Mux8Way` logic maps very cleanly onto a `Mux8Way` chip,
	but, since it wasn't already implemented in previous projects, a
	messy workaround approach was taken.
	-Now, reimplement it with the `Mux8Way` added in 89a87c8.