correct EDNS responses (#96)

Tests updated as well and all the middleware. And Prometheus renamed to
metrics (directive is still prometheus).

middleware/chaos/chaos.go

@@ -43,6 +43,7 @@ func (c Chaos) ServeDNS(ctx context.Context, w dns.ResponseWriter, r *dns.Msg) (
 		}
 		m.Answer = []dns.RR{&dns.TXT{Hdr: hdr, Txt: []string{trim(hostname)}}}
 	}
+	state.SizeAndDo(m)
 	w.WriteMsg(m)
 	return 0, nil
 }