SteveSanderson/knockout — pull request #320 by hartzler (2012-02-09 21:21:27+00:00)
Title: add changed event that passes both old and new values to the willMutate call

We needed this for a versioning interface and we wanted to log both the old and new values, couldn't figure out how to do this, so we hacked this in. Is there a better way we should be doing this?