Moving to Gunicorn - add production requirements
Minor Django version upgrade (keep in sync with 1.4-branch)
Pin down django-debug-toolbar version
Restructure settings

* Rename base.py to common.py (consistent with requirements structure)
* Separate settings files for development/production environments
* __init__.py "nuked", settings module must be spesified by using
  DJANGO_SETTINGS_MODULE environment variable
Load environment variables from env/, use dev settings as default
Upgrade django-reversion to 1.6.6 (compatible with Django 1.4.4+)