Consider using optcarot video and input drivers

[chesterbr]

Optcarot has nicely wrapped a few Gosu alternatives (such as SDL2 and sfml as "video drivers".

It would be nice to provide at least one alternative to Gosu. It would be trivial to implement the equivalent of those as a ruby2600 boot script (like we do for JRuby - AWT/Swing?), but a more interesting alternative would be to include optcarrot as a dependency and reuse the drivers for video and input (we don't implement audio yet).

It depends on how NES-specific the interfaces are, of course. The video one, for example, seems to receive a single-dimension array of pixels (not sure if NES palette or RGB), to which we could quickly convert a frame.