This should have been part of commit 70cc64ee.

This allows the same model to be forward and reverse geocoded and still
provide a geocodable address though a non-attribute method. Also raise
an exception if sufficient configuration is not provided.

Move all network/lookup-related methods into it.

Move some methods into it (organize!).

Stop allowing full :conditions option to near_scope_options (was
deprecated, now it's gone). Update installation documentation.

Should be slightly faster and we avoid an ugly REXML require statement.

Was using version 2. Version 3 no longer requires an API key so this is a big
improvement to the getting started experience.

This makes the tests Rails 3 compatible. Adding /core_ext is necessary
or we don't have access to the class_inheritable_reader method.