newrelic: log country of each request in newrelic.

Log the country of each HTTP request in NewRelic. Uses the CF-IPCountry
header set by Cloudflare.

test/unit/session_loader_test.rb

@@ -10,6 +10,7 @@ class SessionLoaderTest < ActiveSupport::TestCase
       @request.stubs(:cookie_jar).returns({})
       @request.stubs(:parameters).returns({})
       @request.stubs(:session).returns({})
+      @request.stubs(:headers).returns({})
       SessionLoader.any_instance.stubs(:initialize_session_cookies)
     end