spin-sync 0.3.2

Synchronization primitives using spinlock. The interface resembles std::sync. The constructors of public structs are const; i.e. it is possible to declare static Mutex<T> as long as T can be build statically.
Documentation 
# How to Version Up

1. Make sure the changes are merged into master branch.
1. Create 'version\_up' branch and checkout there.
1. Regenerate the documentation.
    1. `git rm -rf docs`
    1. `cargo doc`
    1. `mv target/doc docs`
    1. `git add docs`
    1. `git commit -m 'Regenerate documents'`
1. Update CHANGELOG.md and commit.
1. Update "package.version" in Cargo.toml and commit.
1. Update README.md using `cargo readme > README.md` .
1. Merge branch 'version\_up' into master.
1. Create a new version tag.
1. Reset 'docs' branch to 'master'
1. Push master, docs, and the new tag to origin.
1. Check "https://wbcchsyn.github.io/spin-sync-rs/spin\_sync/"
1. `cargo publish`