Create simple ip address checker service

In order to run IP circuit isolation tests we have been using ifconfig.me. We use it, because it has a wildcard DNS setup and we can check that test1.ifconfig.me/ip and test2.ifconfig.me/ip return the same IP address.

The problem is that, depending on the exit node we get `403 Forbidden` errors, which makes the tests fail intermittently.

It would be nice if we could set up our own service for this. We need at least two different subdomains that return the a plain text IP address. That is all.

Here is an example in PHP, which might be the easiest one to setup:

<?php
echo $_SERVER['REMOTE_ADDR'] . "\n";