Change freegeoip default host.

Reverting back to freegeoip.net (from freegeoip.io) as
it appears to be the intended default host (see:
https://github.com/fiorix/freegeoip/issues/165).

lib/geocoder/lookups/freegeoip.rb

@@ -50,7 +50,7 @@ module Geocoder::Lookup
     end
 
     def host
-      configuration[:host] || "freegeoip.io"
+      configuration[:host] || "freegeoip.net"
     end
   end
 end