previously the mapquest service was relying on an outdated url
that was just defering to the Nominatum service. This commit
brings in supported Mapquest API support for v1 of their API.

It supports the open (free) tier of the API along with the
licensed version of the service.

The version_x_results methods will return nil in case of an error. We
need to detect that and not execute that branch of the 'if' statement.

This fixes issue #256.

Auto-detect which one is being used. It's necessary to continue
supporting 1.0 because of the existing data in people's caches.
See discussion: http://github.com/alexreisner/geocoder/pull/307

This provides a sort of poor man's SQL escaping to prevent injection
attacks. Note that the latitude and longitude column names are not
escaped, but those values should be coming from app configuration and
hence should be safe.

Need to be testing that it works without additional requires.

For readability.

Extend with self so we can private methods are actually private.

"Results" key is now "Result" and is not an array when only one result.
Update code and response fixtures to reflect this.

This fixes issue #305.

"Results" key is now "Result" and is not an array when only one result.

Reduces code duplication.

There is no :method option.

This fixes issue #260.

This addresses issue #199 and is more directly a response to the
excellent comments from github.com/zetetic on commit 1b658304.

Autoexpire cache

This change will call the writer methods defined on an AR model, if they're
implemented, instead of going behind their back. This also avoids a rails 3
deprecation warning, if the named attributes aren't actually database
attributes.

do not redefine "type" method

it is better and faster