Experiment with @wuest's 6502 emulator

[olefriis]

Currently, sidtool relies on an atrocity of a gem I made for simulating the MOS 6510 CPU: https://github.com/olefriis/mos6510. That gem wraps a piece of JavaScript from https://github.com/jhohertz/jsSID. This is done with the mini_racer gem which wraps a V8 virtual machine. It's clearly overkill for solving this problem.

Additionally, this is causing issues for people installing sidtool. So it would be interesting to try out a pure-Ruby solution. Incidentally my awesome colleague @wuest has implemented a MOS 6502 simulator (which is, for all practical purposes, the same as a MOS 6510 emulator): https://github.com/wuest/livestream-6502-emu

This PR just pastes all of the other repository into this. It's really not nice, but meant for experimenting.

[olefriis]

This PR is very slow compared to master, unfortunately.

master:

$ time ruby -Ilib bin/sidtool ../c64-music-presentation/C64Music/MUSICIANS/D/Daglish_Ben/Last_Ninja.sid -o last_ninja.midi --format midi
Processed 15000 frames
ruby -Ilib bin/sidtool  -o last_ninja.midi --format midi  3.09s user 1.03s system 106% cpu 3.878 total

This branch:

$ time ruby -Ilib bin/sidtool ../c64-music-presentation/C64Music/MUSICIANS/D/Daglish_Ben/Last_Ninja.sid -o last_ninja.midi --format midi
[...]
Processed 15000 frames
ruby -Ilib bin/sidtool  -o last_ninja.midi --format midi  48.73s user 0.19s system 99% cpu 48.986 total

[wuest]

Yeah it's not a huge surprise that this is way slower - speed absolutely was not one of the primary concerns for this project. It should be easy enough to rewrite with speed in mind (though I wonder if ruby is going to beat V8 regardless)