Beta pre-release version to test out style (mostly) preserving TOML parser.

You can install this with cargo install cargo-edit --vers 0.3.0-beta.1 (add --force to overwrite an older version).

Changes

• Don't mess up Cargo.toml structure too much (#181)
• Add proxy support via env variable (#179)
• Improved error handling (#167)
• Lots of other improvements

First time contributors

Thanks @ibabushkin!