Add browse page

A few components here:

- the actual browse page
- a new model to contain a summary for each address, which is viewed on the browse page
- a script to populate the db with the above summaries (probably run once/day by cron job in production)
- tests!
We had them normalized for police/fire calls on their way into the database, so that _should_ happen not-that-often. Otherwise, no update on that at all.