Renum Moved to Github

Chris O'Meara recently contributed a fix to make constantize_attribute handle nil values sanely. (Did you know "".constantize # => Object? I was sure surprised.)

He's using constantize_attribute to persist renum enumeration values in ActiveRecord models, which is the reason I wrote it in the first place. The reminder that these things do get used here and there inspired me to give renum a little late Spring cleaning.

Renum now lives on github and is set up to be gem-packaged with jeweler, which is a lot more elegant than the previous solution (at least in terms of how much extra stuff it puts into source control). Release 1.0.2 is tagged, but it's functionally the same as 1.0.1 (it just lives in a better SCM and has less packaging cruft).