Help needed: vendor files for Prometheus support

These are the vendor files needed for Prometheus support.
I have not been able to figure out how to do this properly with gopkg.

vendor/github.com/miolini/datacounter/response_writer.go

@@ -0,0 +1,45 @@
+package datacounter
+
+import (
+	"bufio"
+	"net"
+	"net/http"
+	"sync/atomic"
+)
+
+// ResponseWriterCounter is counter for http.ResponseWriter
+type ResponseWriterCounter struct {
+	http.ResponseWriter
+	count  uint64
+	writer http.ResponseWriter
+}
+
+// NewResponseWriterCounter function create new ResponseWriterCounter
+func NewResponseWriterCounter(rw http.ResponseWriter) *ResponseWriterCounter {
+	return &ResponseWriterCounter{
+		writer: rw,
+	}
+}
+
+func (counter *ResponseWriterCounter) Write(buf []byte) (int, error) {
+	n, err := counter.writer.Write(buf)
+	atomic.AddUint64(&counter.count, uint64(n))
+	return n, err
+}
+
+func (counter *ResponseWriterCounter) Header() http.Header {
+	return counter.writer.Header()
+}
+
+func (counter *ResponseWriterCounter) WriteHeader(statusCode int) {
+	counter.writer.WriteHeader(statusCode)
+}
+
+func (counter *ResponseWriterCounter) Hijack() (net.Conn, *bufio.ReadWriter, error) {
+	return counter.writer.(http.Hijacker).Hijack()
+}
+
+// Count function return counted bytes
+func (counter *ResponseWriterCounter) Count() uint64 {
+	return atomic.LoadUint64(&counter.count)
+}