Support `+` tag on release list; drop support for raring.

`+` indicates that the release used to be supported, and encourages the user to upgrade. Auto-testing is still
performed on the release.
After a few months, the release should be switched to unsupported (`*`).

raring upstream support was dropped on 27 January 2014 (see https://wiki.ubuntu.com/Releases)

Tested in `2014-03-03_13-58-46_drinkcat_chroagh_drop-raring-support_1`.