- InvalidTXTRDATA error when creating TXT record (closes#94)
- Present() should poll and wait until the status of the record change becomes INSYNC (thanks @oov)
Adds a retry/timeout utility function to dns_challenge.go that may be used in other places
* new ChallengeProvider with Present and CleanUp methods
* new Challenge type describing `http-01`, `tls-sni-01`, `dns-01`
* new client.SetChallengeProvider to support custom implementations