Use QuerySet._fk_val instead of _pk_val on Django>=1.5. Fixes #10.
Skip duplicate_targets bookkeeping on Django>=1.5. Fixes #8.
Merge commit 'e82ad50' into master
Merge commit 'ae9c317'

Conflicts:
	CHANGES.rst
Using the real authors django-setuptest library since he merged my pull request.
Cleaning up the SortedManyToManyField implementation. This breaks compatibility with Django 1.3.
Updating manage.py to work with Django 1.5
Preparing 0.5.0 release.
Refactoring south support tests.
Fixes #9 -- Allow the user to customize the name of the sort-by field of the intermediate m2m relation table.
Adding documentation for sort_value_field_name.