v0.3.0

A lot has happened since the last stable release!

The most important feature sure is that we try to not mess up your Cargo.toml files anymore!
While we are not 100% there yet, cargo add foo should give you much nicer edits now.

Other cool features:

• Add proxy support via env variable (#179)
• Allow simultaneous specification of both version and path
  (thanks, @dherman!)
• Add specific error for a missing crate (thanks, @bjgill!)
• cargo-upgrade now supports --precise, --dry-run, and has nicer output