Add pkg.rs for rustpkg support and change fail! to die!
Merge pull request #26 from z0w0/master

Add rustpkg support
Surfaces now track whether they're supposed ot be freed. Fixes #27
Switched fail! out for the more correct die!
Implement `img::load_img` (`IMG_Load` from `SDL_image`).

Because life without transparent images is so boring...