Add a COPYRIGHT file (#223)

Author: joeduffy

Diff for: COPYRIGHT

@@ -0,0 +1,11 @@
+Except as otherwise noted below and/or in individual files, this
+project is licensed under the Apache License, Version 2.0 (see
+LICENSE or <http://www.apache.org/licenses/LICENSE-2.0>).
+
+This project is a larger work that combines with software written
+by third parties, licensed under their own terms.
+
+Notably, this larger work combines with the Terraform AWS Provider,
+which is licensed under the Mozilla Public License 2.0 (see
+<https://www.mozilla.org/en-US/MPL/2.0/> or the project itself at
+<https://github.com/terraform-providers/terraform-provider-aws>).