Merge pull request #1 from greylock/serialize_transients

serialize from memory for transient model instannces
Merge pull request #2 from jessedhillon/master

merge head upstream batteries
Serialize None attribute as None, not an error
Custom logic in the presence of naming conventions

HashableReference's default constraint name is ignored if a naming convention
has been established.
Version bump
Merge pull request #7 from greylock/master

serializing an object with an attribute set to `None`