chore: copyright

Author: genesor

contrib/net/http/roundtripper_test.go

@@ -1,3 +1,8 @@
+// Unless explicitly stated otherwise all files in this repository are licensed
+// under the Apache License Version 2.0.
+// This product includes software developed at Datadog (https://www.datadoghq.com/).
+// Copyright 2016 Datadog, Inc.
+
 package http
 
 import (