fixes regression in using an attribute introduces in 318e93a

A fix for serializing an attribute declared as serializable intended for the rails 2.3 branch was applied without taking note of the altered attribute name introduced in the rails 3 branch. The purpose of the serialization fix is still valid though. So this commit fixes both, the serialization bug 318e93a intended to fix as well as the regression introduced by 318e93a
Merge pull request #65 from opf/feature/rails3_fix_journal_migration

fixes regression in using an attribute introduces in 318e93a