After every scraper run automagically vacuum the sqlite database

[mlandauer]

This is to ensure in cases where people are deleting and adding lots of data that we don't get the database size to balloon out of control.

Also, this is better that running vacuum as a cron job because it will constantly keep the space under control and we can atomically swap out the updated and vacuumed databased with the original so there's no chance of the vacuum interfering with a read going on on the database.