Updated changelog
Freezying version to v1.2.0
Removed explicit requirement of Django version from setup.py

guardian should work with older Django too,
auth backend was part that could work with 1.2
or later, however it does not necessary be used
Brought back testing Django 1.2
Revert "Removed deprecated assign shortcut"

This reverts commit 73aa744d8eda0a7de2fd4fcb7926e145181f2f00.

Conflicts:
	guardian/tests/shortcuts_test.py

We don't want to introduce backward incompatible changes before new
major release.
Deprecated shortcuts should be removed in next major release
Merged from release-12