Update README.md

Need increased specificity to support other MaxMind packages.

Also split single rake task into several.

This should have been part of bd37a240.

test that :smarty_streets interprets zipcode results

Raise exceptions on HTTP 400, 402

This is relevant for SmartyStreets, and seems like a good idea in
general (possibly supported by other APIs).

Also much code cleanup.

Add geocod.io exceptions

instead of #latitude and #longitude. This fixes #613.

Conflicts:
	test/services_test.rb

add over quota exception handling for nominatim