Tracking issue for libz blitz evaluation

[KodrAus]

The original discussion and guidelines checklist

Also see: the semver_parser tracking issue

We've extracted the following contribution opportunities out of the libz blitz evaluation of semve:

• Use ? instead of unwrap in examples
• Document error cases on Version::parse
• Document error cases on VersionReq::parse
• Turn references to other semver items into links
• Add keywords and categories to Cargo.toml
• Add html_root_url attribute to crate root
• Make error types non-exhaustive
• Make fields on Version private
• Support range sets
• Rename VersionReq to Range

We need your help!

• If you'd like to do one of these just leave a comment on the issue saying you're working on it.
• If it's been a little while since an issue was claimed and there isn't a PR yet then feel free to re-claim it.
• If you wanted to work on something but just didn't get around to it then don't feel bad! That's ok, and if you'd like to try something else we've got plenty more contribution opportunities. Just reach out on gitter

Some of these issues need more discussion so we can work out bigger design questions and put together mentoring instructions. It'd be great if you could leave your thoughts on those issues!