new formula: id3ed

[id3ed](http://code.fluffytapeworm.com/projects/id3ed) is an ID3 tag editor for mp3 files. The latest version is over 10 years old, so I’m not sure it fits Homebrew requirements, but it’s stable and [known](http://www.tldp.org/HOWTO/MP3-HOWTO-13.html) (it’s available on several Linux distributions).