Update changelog

CHANGELOG.md

@@ -32,6 +32,13 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/)
       of the public ip
   - `monitor_machines` periodic task runs once each night rather than every 30 minutes
   - Subspace is replaced by Ansible's PlaybookCLI for instance deployment ([#631](https://github.com/cyverse/atmosphere/pull/631))
+  - Added timeout of 5 sec to tas api for user validation, and refactored to
+    make validation more explicit in the absence of the old selected_identity
+    notion ([#639](https://github.com/cyverse/atmosphere/pull/639))
+
+### Removed
+  - Removed references to selected_identity
+    ([#639](https://github.com/cyverse/atmosphere/pull/639))
 
 ### Fixed
   - `application_to_provider` was using an invalid method in Glance Client v1 to upload image data ([#618](https://github.com/cyverse/atmosphere/pull/618))