Merge pull request #10 from bvssvni/master

Upgraded to latest Rust-Empty
Merge pull request #11 from bvssvni/master

Upgraded to latest Rust + Rust-Empty
Updated .gitignore to include Cargo.lock
Updated to latest Cargo and changed package name to sdl2_mixer
Merge pull request #12 from EnvisionRed/master

Update to latest Cargo and change package name.
Upgrade to latest Rust (breaking changes)

* Removed unused field on README.md
* Replaced `static` with `const`
* Using new `cfg` annotation
* Using ELEPHANT_CASE for InitFlag
* Removed `visible_private_types`