Was causing:

    NoMethodError: private method `include' called for
      ActionDispatch::Request:Class

* handles unreachable network exception

* adds network error class

* tests unreachable host exception handling

Change SmartyStreets Zipcode API.

Smarty street's new zipcode api endpoint as of 26 March 2016.
http://status.smartystreets.com/incidents/4hjpfqh9q2k7

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.

try Rack::Request if ActionDispatch::Request is not defined, fixes #1060

Wasn't testing what it claimed to be testing.

Intended to fix #1048.

add `source_country` parameter for esri geocoder

Add Method for Merging Lookup Configuration

ESRI lookup now uses this method.

fix merging esri config when generating a token

This should improve readability and make testing easier as it separates
the various tasks into separate methods.

Add Mapzen reverse geocoding

fix reference to EsriToken, avoid using rails .minutes

Disable SSL v2 and v3 if ssl enabled

* Support for a custom telize endpoint

* fix path

Add result_type as option for google lookup

The #latitude and #longitude methods are defined in the Base lookup. The
intention is that subclasses implement #coordinates only, as it results
in less code duplication.