Add Python 3 to tox and drop Django 1.2 and 1.3
Add Python 3 to travis and drop Django 1.2 and 1.3
Fix repr tests for Python 2 (no string comparison)
Note Python/Django version support in CHANGES.rst
Remove datetime imports unused by Django 1.4+
Update supported Python/Django versions in README
Add supported Python versions to classifier troves
Add minimum required Django version to setup
Remove reduntant "as" in import
Remove with_statement import (was needed for 2.5)
Fix deprecated assertion methods in tests