Example test vector

[MelindaShore]

From Shumon: The example test vector is the original one from Langley's text right? That name, www.dnssec-exp.org, doesn't actually exist anymore, so we should probably use another name. That example also ends in a TXT record at that name, because I believe the TLSA record didn't exist when Langley wrote the original draft, and he stuffed some cert related info into a TXT record. Our newer example should be one that has a TLSA record I think