Added integration_tests app to example project

- added integration_tests to tox
Cache content types for classes.
Change get_objects_for_user so it creates much more efficient queries when not using groups.
Change get_objects_for_user so it creates much more efficient queries when not using groups.
Whoops.
Add test to give get_objects_for_user 100% coverage again.
Merge faster_get_objects_for_user. Fix conflict.
GuardedModelAdmin patch for supporting USERNAME_FIELD
error message fixed, tests run when "testsettings.py" is used
Merge branch 'master' of https://github.com/lukaszb/django-guardian
Extended development docs
Added watch-docs.sh
Explain why devel is now default branch
Some clarifications on supported versions
It's 2013
Changed "tunning" to "tuning".

Corrected spelling of "tuning".
Merge pull request #175 from jwegis/patch-1

Changed "tunning" to "tuning".
Added John to AUTHORS file
Updated test for postgresql
Added wheel support at setup.cfg