Types: convert strings back to symbols when reading from the database
Fix version detection of Rails 4.1.0.rc1
Bug fix: Dirtiness wasn't properly cleaned after a database read
Removed doc.attributes= accessor

It's too weird. We need to cleanup the old attributes, but we should keep the id
attribute, and we might also need to run the default value assignments.
This semantics is a bit hard to think about.
Run the uniqueness validator with distributed locks