Refactored client options

Fixed default User-Agent string not being set.

geziyor_test.go

@@ -220,7 +220,11 @@ func BenchmarkRequests(b *testing.B) {
 	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 		fmt.Fprint(w, "Hello, client")
 	}))
-	ts.Client().Transport = client.NewClient(client.DefaultMaxBody, false, client.DefaultRetryTimes, client.DefaultRetryHTTPCodes, "").Transport
+	ts.Client().Transport = client.NewClient(&client.Options{
+		MaxBodySize:    client.DefaultMaxBody,
+		RetryTimes:     client.DefaultRetryTimes,
+		RetryHTTPCodes: client.DefaultRetryHTTPCodes,
+	}).Transport
 	defer ts.Close()
 
 	// As we don't benchmark creating a server, reset timer.