It has been deprecated: announcement.
Is there any functionality you would require from another library before this would be possible?
Great! We're only using it for base64 and hex. Any recommendations?
I read the end of the discussion, and fixed this issue with patch #AfoYhoYRLkGUdRRe1zoUcVEhmA8SA0Mvg5eAvAxaYIZmhD__N5PDKKvgy2FblYaD_gZJCZOwnglMzLdsTLPEzU0
Thanks for reporting, I was really waiting for the the serde/rustc-serialize situation to end, this change makes me happy.