Parse version numbers optionally without the patch version specified
Parse version numbers optionally without the patch version specified

Fixes #794.

rust-lang/rustup,nodakai/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,nodakai/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,rust-lang/rustup,rust-lang/rustup,nodakai/rustup.rs