* Add support for Ed25519 DNSSEC signing from RFC 8080
Note: The test case from RFC 8080 has been modified
to correct the missing final brace, but is otherwise
present as-is.
* Explain why ed25519 is special cased in (*RRSIG).Sign
* Explain use of ed25519.GenerateKey in readPrivateKeyED25519
* Add dep
This is PR #458 with the dependency added into it.
Miek Gieben