Fix parsing versions which contain hyphens

Before this release, crates with versions like v0.2.1-alpha.1 would crash with a PackageSpec "suffix" parse error.

This release contains precompiled binaries for common platforms.

Other Changes

• Update dependencies (clap-cargo -> 0.15, cargo_metadata -> 0.19)
• Avoid trailing newline in pkgid parse error
• Improve readme and fix typos