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)
I like this syntax better:

```python
group_list = (Datas.objects(host=hostName, project_name=projectName)
                   .filter(date__gte=startdate)
                   .order_by('project_name'))
```