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`.
2^16 == 18 ;)

(I'll admit i only caught it when Rust complained ```expected `[u8, .. 65536]`, found `[u8, .. 18]` ```)