Make days and months also optional in date parsing
Move some code
Add test for _parse_date
slices is renamed bins, which is the standard name for histogram categories
Add datetime generation between min and max to fill with 0 values
Update client side to handle new aggregation level
Put relativedelta import with other not-standard-library imports
Use operator.itemgetter for standard lambda function access
Refactoring in density while loop
Add dateutil to dependencies
Fix limit bug
Add tests
Fix detection problem when scanning fields
Some function name changes
Remove "s" for aggregation levels
Fix tests