*.rs: fix compile error under rust-nightly
add demo bin to Cargo.toml
Merge pull request #17 from andelf/master

Fix compile error under rust-nightly
Fix demo with rustc nightly
Merge pull request #18 from jdeseno/fix-demo-for-nightly

Fix demo with rustc nightly
fix build error: rust-sdl2 Renderer change; rust fail! rename to panic!
Merge pull request #20 from andelf/master

fix build error: rust-sdl2 Renderer change; rust fail! rename to panic!