fixed all migrations for supporting custom user models
use get_username function when appropriate
Revert "use get_username function when appropriate"

This reverts commit 4299078f36223f1990cb69624585bba850e181ac.
Changes not supported in django 1.4
removed django-mailer from hard dependencies
Merge pull request #71 from hovel/custom_user_model

Custom user model support
removed pytils from hard dependencies
removed sorl.thumbnail from hard dependencies
Merge remote-tracking branch 'origin/master' into remove_dependencies

Conflicts:
	docs/updates.rst
	pybb/models.py
	pybb/templates/pybb/avatar.html
	pybb/templates/pybb/post_template.html
	pybb/templates/pybb/user.html
More smarter load of thumbnail library

because django by default loads all custom libraries before page rendering, we have to use more smart loading of thumbnail library. Choosed template tags from https://bitbucket.org/jaap3/django-friendly-tag-loader to accomplish this task
removed django-pure-pagination from hard dependencies
Merge branch 'remove_dependencies' into python3

Conflicts:
	setup.py