Allow dyndnsd to use address from X-Real-IP

spec/spec_helper.rb

@@ -6,3 +6,7 @@ require 'rack/test'
 require 'dyndnsd'
 require 'support/dummy_database'
 require 'support/dummy_updater'
+
+RSpec.configure do |config|
+  config.expect_with(:rspec) { |c| c.syntax = :should }
+end