chore: Update CHANGELOG.rst

Author: scottarc

CHANGELOG.rst

@@ -2,6 +2,23 @@
 Changelog
 *********
 
+2.0.0 -- 2020-09-24
+===================
+
+New Features
+------------
+
+* Updates to the AWS Encryption SDK. 2542b58
+
+  This change includes fixes for issues that were reported by Thai Duong from Google's Security
+  team, and for issues that were identified by AWS Cryptography.
+
+  BREAKING CHANGE: AWS KMS KeyIDs must be specified explicitly or Discovery mode explicitly chosen.
+
+  Key committing suites are now default. CommitmentPolicy requires commitment by default.
+
+  See: `Migration Guide <https://docs.aws.amazon.com/encryption-sdk/latest/developer-guide/migration.html>`_
+
 1.7.0 -- 2020-09-24
 ===================