Summarize data

Please, check my code!
I forgot to include some kind of readme.st. To test custom command:
python manage.py summarize [date YYYY-MM-DD] [--nodeletion]
If you pass no parameters it summarizes current date minus 15 days (single day and no a 15-days period)
You should explicitly add the dependencies. E.g. `django-werkzeug-debugger-runserver==0.2`. Add a comment about which packages are dependencies of what.