lat_lng search (now with tests)

I made sure that this passes all tests (at least for search - a bunch of the other tests are broken), and added some new tests.

Also, renamed the parameter to lat_lng from geo, which I agree makes more sense.
Please style this line this way: `coords = lat_lng.split(',').map { |f| Float(f) }`
Minor Ruby Style Guide issue here, but we're picky :smile: