add list_hosted_zones request mock

lib/fog/aws/requests/dns/list_hosted_zones.rb

@@ -49,6 +49,49 @@ module Fog
         end
 
       end
+
+      class Mock
+
+        def list_hosted_zones(options = {})
+          if options[:max_items].nil?
+            maxitems = 100
+          else
+            maxitems = options[:max_items]
+          end
+
+          if options[:marker].nil?
+            start = 0
+          else
+            start = self.data[:zones].find_index {|z| z[:zone_id] == options[:marker]}
+          end
+
+          zones     = self.data[:zones].values[start, maxitems]
+          next_zone = self.data[:zones].values[start + maxitems]
+          truncated = !next_zone.nil?
+
+          response = Excon::Response.new
+          response.body = {
+            'HostedZones' => zones.map do |z|
+              {
+                'Id' => z[:zone_id],
+                'Name' => z[:name],
+                'CallerReference' => z[:reference],
+                'Comment' => z[:comment],
+              }
+            end,
+            'Marker' => options[:marker].to_s,
+            'MaxItems' => options[:max_items].to_s,
+            'IsTruncated' => truncated.to_s
+          }
+
+          if truncated
+            response.body['NextMarker'] = next_zone[:zone_id]
+          end
+
+          response
+        end
+
+      end
     end
   end
 end