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!
There's a lot of DRY potential here... would you be up for storing [7, 30, 90, 365] somewhere and working with them (and 7*2, 30*2, etc.) throughout?