Allow requesting shelters based on address

[dstuck]

In terms of next steps it seems like the next major upgrade to functionality would be to allow passing address information rather than just zip code to find the closest shelters. One impact of changing this would be limiting the search to a single location, but I think that's searching multiple addresses from one text isn't that important if you can specify precise location rather than zip code.

This would require depending on geocoding which is something that I wanted to bring up some discussion on since my experience with geocoding is very limited. node-geocoder seems to support quite a few apis so hopefully one would be workable for our use case?

To start with I thought I'd work on refactoring the shelter_finder module to go through a lat/lon interface rather than requiring zip code as an input.

[dstuck]

@nihonjinrxs What do you think about me starting out by making the shelter finder interface through lat/lon coordinates