Remove everything except README

Why? Because:
1) It's written 2/3 of year ago
2) Thus it's mostly crap
3) It makes use of pre-GLFW 3, so it has to be rewritten
4) It's painful to look at code so I won't
5) Making new awesome game right > dealing with old wrong useless stuff
Add empty SDL2 window
Add assertf function and event loop