Cargo.toml: Change documentation to point to newest version
Cargo.toml: Change documentation to point to newest version

So the documentation link doesn't have to be manually updated for new
releases, but rather will always point to the newest version.

carllerche/mio,mneumann/mio,carllerche/mio,mneumann/mio,murarth/mio,fuchsia-mirror/third_party-mio,fuchsia-mirror/third_party-mio