Add Windows requirements section.  Fixes #54.
Add Windows requirements section.  Fixes #54.

Cobrand/rust-sdl2,vadixidav/rust-sdl2,Cobrand/rust-sdl2,Cobrand/rust-sdl2,Rust-SDL2/rust-sdl2,Rust-SDL2/rust-sdl2,Rust-SDL2/rust-sdl2,andelf/rust-sdl2_mixer,AngryLawyer/rust-sdl2