Database refactor

These commits should complete the necessary database refactor we talked about earlier. It also adds the foundation for recurring dates. I haven't tested all the endpoints (such as market details, since this isn't hooked up to anything in the front end), but I've gone through our use cases, and location creation/editing/deletion, and item creation/editing/deletion seem to be working. The vendor details page and all endpoints associated with it have also been updated to reflect the new data model.

Tags are also in place, though the views have not yet been updated to do anything with them. I don't mind to take a look at this once someone jumps on tags for the front end.

The Google Geocoding API has also been added so that we can store latitude and longitude in the database. We're also now scraping all address information directly from the API so that users don't have to manually enter it. The way this is being done is pretty hacky, since the API returns terribly formatted data, but it's worked so far for all North American addresses I've tried. 

Also, addVendor.sh has been updated so creating Vendors should be as easy as running that script still.

It would be great if everyone could test this thoroughly and let me know if there's anything I missed. It still feels fragile to me, and I'm sure there are plenty of things I've overlooked.

Make sure you run **sudo** pip install django-taggit after pulling :).