ipv6-only website check broken

Keybase fails to prove a website, if said website has _only_ an AAAA record:
## Example:

host penguinfriendly.de is IPv6-only:
penguinfriendly.de has IPv6 address 2001:7b8:2ff:1a3::2

... and accessible:
wget http://penguinfriendly.de
--2014-04-05 18:54:26-- http://penguinfriendly.de/
Auflösen des Hostnamen »penguinfriendly.de (penguinfriendly.de)«... 2001:7b8:2ff:1a3::2
Verbindungsaufbau zu penguinfriendly.de (penguinfriendly.de)|2001:7b8:2ff:1a3::2|:80... verbunden.
HTTP-Anforderung gesendet, warte auf Antwort... 200 OK
Länge: 4673 (4,6K) [text/html]
[...]
2014-04-05 18:54:26 (66,1 KB/s) - »»index.html«« gespeichert [4673/4673]

... but keybase thinks otherwise:

┌─[bbu@hobbes]─[~]
└──╼ keybase prove web penguinfriendly.de
error: Failed to find a connection to penguinfriendly.de (error #229)

Start by reproducing the failure with `keybase prove web penguinfriendly.de` and compare it with the successful `wget` request shown in the issue. Trace the web-proof connection path that handles the hostname and IPv6 address. Done means an IPv6-only website with only an AAAA record can be proved successfully.

Written by the indexing model from the issue text.