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!
When there are multiple businesses at one address, I think ideally we'd display their names all together but we wouldn't store them all together, to maintain flexibility in case we wanted to be able to separate them out/sort by them/etc. later on. What do you think?