Fix comments, tests, and formatting

authorizer/dns.go

authorizer/dns_test.go

current/activity.go

current/activity_test.go

excludedRounds/set.go

excludedRounds/set_test.go

fact/fact.go

fact/factList.go

fact/factList_test.go

fact/fact_test.go

fact/type.go

fact/type_test.go

format/fingerprint_test.go

format/message.go

format/message_test.go

knownRounds/knownRounds.go

knownRounds/knownRounds_test.go

knownRounds/uint64Buff.go

knownRounds/uint64Buff_test.go

nicknames/isValid.go