3.0: New Database Structure

• Split database table list_stats into email_list and list_stats. The new configuration supports multiple analyses of a given list, each with its own timestamp, for comparing statistics over time. This is a breaking change, as the two database structures are incompatible and data needs to be manually migrated across (and seeded with analysis timestamps).
• Updated tasks.py to interface with the new database models.
• Updated the Celery Beat tasks which updated known lists in the background. Instead of updating a random portion of the database every night, now searches for lists whose most recent analysis is more than a month old and generates a new analysis for those lists.
• Updated test suite.