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!
Lines 32 and 36 use the same list of numbers that could conceivably be passed in... I'm being persnickety, I know, but noting it in case you'd like to DRY it up.