DNS spoofing to captive portal on non-internet connected networks

To test:

0. Install this version of commotion-splash on a router (using this Makefile: https://github.com/opentechinstitute/commotion-splash/blob/dns-spoof/openwrt/Makefile)
1. bring up a node as an internet gateway (and with this version of commotion-splash, obvio), and connect to it. Open a browser and go to any page; it should captive portal you.
2. run "dig commotionwireless.net" from your computer, and it should give you our server's IP address: 209.66.96.69.
3. Now unplug the ethernet connection to the router's PoE jack, so it is no longer connected to the upstream gateway.
4. Open another browser, and go to redemmas.org. You should still get captive-portaled.
5. To double-check, run "dig indyreader.org" from your computer, and it should give you 1.2.3.4 as the IP address. Shazam!