nand2tetris project 5: add notes.

books/nand2tetris/notes/(5_computer_architecture.md, img/von_neumann_architecture.png)
	-Add notes for the 5th chapter ("Computer Architecture") of
	nand2tetris.
nand2tetris project 5: add Memory.hdl.

books/nand2tetris/projects/5_computer_architecture/Memory.hdl
	-Add a `Memory` chip implementation.
nand2tetris project 5: add CPU.hdl, Jump.hdl.

books/nand2tetris/projects/5_computer_architecture/(CPU, Jump).hdl
	-Add a functional `CPU` chip, with a supplementary `Jump` chip.
nand2tetris project 5: add Mux4Way.hdl.

books/nand2tetris/projects/5_computer_architecture/Mux4Way.hdl
	-Add a documented implementation of a `Mux4Way` chip.
	-Will be used to implement a `Mux8Way` chip, to reimplement
	`Jump`.
nand2tetris project 5: add Mux8Way.hdl.

books/nand2tetris/projects/5_computer_architecture/Mux8Way.hdl
	-Add an implementation of a `Mux8Way` chip.
	-Will be used to reimplement the `Jump` chip.
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.
Add API documentation comment to Jump.hdl.

books/nand2tetris/projects/5_computer_architecture/Jump.hdl
	-Document the Jump chip's API.
Rewrite CPU API documentation comment.

books/nand2tetris/projects/5_computer_architecture/CPU.hdl
	-Rewrite the `CPU` chip's API documentation comment in the same
	format as all of the others.
	-Strip `IN`/`OUT` pin documentation comments.
nand2tetris project 5: add Computer.hdl.

books/nand2tetris/projects/5_computer_architecture/Computer.hdl
	-Implement the `Computer` chip, completing chapter 5.
Merge branch 'books/nand2tetris.5_computer_architecture' into books/nand2tetris

books/nand2tetris/notes/5_computer_architecture.md, books/nand2tetris/projects/5_computer_architecture/
	-Complete chapter 5, "Computer Architecture", of nand2tetris.