v0.12.0

• fix crash #15 because a bad answer decoding
• fix issue #14 json log duplicates
• feature: missing rdata in answers #9, support mx, soa, ns, txt, cname and ptr
• fix issue prom2json failed #12 - bad metrics format
• feature: get the version of the go-dnscollector binary #10, new version argument
• feature: rdata for format: text #9 ,support first dns answer only