Add license information to README

Author: Stephen Pinkerton

README.md

@@ -194,4 +194,6 @@ If you find an issue with this package and have a fix, please feel free to open
 
 ## License
 
-TBA
+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 2019 Datadog, Inc.