Expand audit unicode method
Stop tracking instance and change type to a set
Factor out model_hasattr
Replace call to full_clean() with clean()

full_clean() does too much built-in django validation to be
compatible with the changes made in the audit system.
Add new-object creation support for pending edits

Fixes #82 on github.
Phase out god_user from tests

god_user is no longer necessary now that the the audit system
does not track instances and uses ids to determine create
privileges.
Catch exceptions to support apply_change instead of setattr