support for opencagedata optional parameters

LocationIq # for classes
location_iq # for config

* handles unreachable network exception

* adds network error class

* tests unreachable host exception handling

SmartyStreets is permanently changing their ZIP Code API endpoint by
June 22 at 9am Mountain Time.  The legacy API endpoint is available
until the 22nd.

This change basically changes the API endpoint and updated the tests to
reflect the change.

Wasn't testing what it claimed to be testing.

Intended to fix #1048.

ESRI lookup now uses this method.

* Add ip-api.com (ip lookup) support

This service returns better coordinates for Europe than other free ip lookup services available in geocoder.

* Clean the results class

Remove default responses for fields.

* Remove checking fields in url query

API already handles unknown fields, so this check is unnecessary.

* Add a test for using parameters directly in search method

* Use proper domain name

Use pro.ip-api.com domain in case when api key is in use, otherwise just ip-api.com.

* Handle invalid api key

* Add forsaken fixture

* Make uniform an invalid key handler with the other geocoder lookups

* Add ip-api.com (ip lookup) support

This service returns better coordinates for Europe than other free ip lookup services available in geocoder.

* Clean the results class

Remove default responses for fields.

* Remove checking fields in url query

API already handles unknown fields, so this check is unnecessary.

* Add a test for using parameters directly in search method

No longer needed now that :yahoo lookup is gone.

Test that geocoded? returns false when only a single coordinate is present