Add Copyright Header

Summary: Pull Request resolved: https://github.com/facebookresearch/d2go/pull/24

Reviewed By: wat3rBro

Differential Revision: D27127642

Pulled By: zhanghang1989

fbshipit-source-id: 18bc3c2fa05232cacc778925db6b7dcea99b108c

tools/benchmark_data.py

 #!/usr/bin/env python3
+# Copyright (c) Facebook, Inc. and its affiliates. All Rights Reserved
 """
 Tool for benchmarking data loading
 """