Merge Johannes' changes into mine

I tried my best to merge Johannes' changes into what I have been working on.  The directory structure comes from running `cargo new 6502emu --bin`.  There is one unit test that can be compiled with `rustc --test -A dead_code 6502emu/src/main.rs`.
This seems fine.  Plus typing typing 6\<tab\> is more annoying than e\<tab\>.