Add tensorflow notice

mace/third_party/flatbuffers/build_defs.bzl

+# This file is copied from TensorFlow
 # Description:
 #   BUILD rules for generating flatbuffer files.
 
@@ -95,7 +96,6 @@ def flatbuffer_library_public(name,
         visibility=reflection_visiblity
     )
 
-
 def flatbuffer_cc_library(name, srcs, srcs_filegroup_name="",
                           out_prefix="", includes=[], include_paths=[],
                           flatc_args=DEFAULT_FLATC_ARGS,

mace/third_party/flatbuffers/flatbuffers.BUILD

+# This build file is copied from TensorFlow
+
 package(
     default_visibility = ["//visibility:public"],
 )