Opentracing support

vendor/github.com/Shopify/sarama/response_header.go

@@ -0,0 +1,21 @@
+package sarama
+
+import "fmt"
+
+type responseHeader struct {
+	length        int32
+	correlationID int32
+}
+
+func (r *responseHeader) decode(pd packetDecoder) (err error) {
+	r.length, err = pd.getInt32()
+	if err != nil {
+		return err
+	}
+	if r.length <= 4 || r.length > MaxResponseSize {
+		return PacketDecodingError{fmt.Sprintf("message of length %d too large or too small", r.length)}
+	}
+
+	r.correlationID, err = pd.getInt32()
+	return err
+}