Start using third party libraries more

[omarandlorraine]

The amount of time I have to spend on doing my own emulation code is insane here. So I'm doing this experimental branch to move to using more external dependencies; won't that be good?

I'm aware of these things we'll lose:

• stm8 support (I can't find an suitable emulator)
• kr580vm1 support (ditto, but I might be able to make one)
• it may be harder to do PIC support which is something I wanted to do

I'm aware of these things we'll gain:

• Much faster development time
• More complete coverage of the available opcodes, which means things like arrays, loops, and other basics
• Theoretically we can now support self-modifying code (but do we want to?)

[omarandlorraine]

there is a bug in the z80 backend regarding DE-prefixed instructions. It's connected to this issue in the dez80 crate

It's why the tests don't pass

[omarandlorraine]

it should be noted that the merging of this should close #37

[omarandlorraine]

we should make the new dependencies optional so that they depend on enabled features; conditional compilation.

[omarandlorraine]

We probably need better parallelism in the example that is src/main.rs