Http dump performance

gistfile1.txt

```
go test -bench=.
BenchmarkPlain-8           20000             75742 ns/op
BenchmarkDump-8            10000            133477 ns/op
PASS
ok      tmp     3.648s
```

main_test.go

package main_test

import (
	"io/ioutil"
	"net/http"
	"net/http/httptest"
	"net/http/httputil"
	"testing"
)

var rb []byte = []byte(`SERVER RESPONSE SERVER RESPONSE SERVER RESPONSE SERVER RESPONSE SERVER RESPONSE SERVER RESPONSE SERVER RESPONSE`)

func BenchmarkPlain(b *testing.B) {

	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
		w.Write(rb)
	}))
	for n := 0; n < b.N; n++ {
		req, _ := http.NewRequest("GET", srv.URL, nil)
		resp, _ := http.DefaultTransport.RoundTrip(req)
		ioutil.ReadAll(resp.Body)
	}

	srv.Close()
}

func BenchmarkDump(b *testing.B) {
	srv := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		w.WriteHeader(http.StatusOK)
		w.Write(rb)
	}))
	for n := 0; n < b.N; n++ {
		req, _ := http.NewRequest("GET", srv.URL, nil)
		resp, _ := http.DefaultTransport.RoundTrip(req)
		ioutil.ReadAll(resp.Body)
		_, _ = httputil.DumpRequestOut(req, true)
		_, _ = httputil.DumpResponse(resp, true)
	}

	srv.Close()
}