Add Linux/OSX support

[maxton]

This should run in Mono, in theory, except for the audio API. NAudio relies on WASAPI and/or other windows-only libraries to get audio out of the speakers. Look into another audio library. I think maybe PortAudio would be best, I think it has .NET bindings somewhere, otherwise, possible BASS.NET, although that is non-free. If anyone knows of some other audio APIs, I am all ears.

[maxton]

Also test running this in WINE, which may work with NAudio directly

[JunielKatarn]

I'm currently researching the "Mock" audio player temporary fix.
Turns out only the _waveForm's Play/Pause/Stop methods end up calling Windows-exclusive APIs.

I expect to have a PR by the end of the weekend.