Django 1.7 BooleanField default changed to None

Django 1.6 BooleanField default value is False. This ensures that
Django 1.7 system check warnings get silenced.
Merge pull request #54 from boardman/master

Fix migrations when using 1.5+ custom user model.
bump version
Update decorators.py

Add Boolean flag "DJANGO_TWILIO_BLACKLIST_CHECK" to turn off blacklist in setting
Update decorators.py

-CaMeL casing error fix
Update utils.py

Catch all errors resulting from blacklist checking, not just one exclusive case
Merge pull request #53 from clarkbarz/django-1.7-system-check

Django 1.7 BooleanField default changed to None
Merge pull request #55 from jvankoten/master

Add ability to turn off blacklist checking in Django settings
Flake8 linting
Adding settings and contributors to docs
Bump version
Update django-nose for development environment
Docs updates for 0.5.3
WIP on django 1.7 support
Phone number field update to support Python 3
Removed compat.py, AUTH_USER_MODEL in models.py
Initial django 1.7 migration compatibility
Update to support South 1.0
Update South version
readme tweaks