CHANGELOG.md in event_sourcery-postgres-0.3.0 vs CHANGELOG.md in event_sourcery-postgres-0.4.0

@@ -4,9 +4,22 @@
 The format is based on [Keep a Changelog](http://keepachangelog.com/)
 and this project adheres to [Semantic Versioning](http://semver.org/).
 
 ## [Unreleased]
 
+## [0.4.0] - 2017-6-21
+### Changed
+- Reactors store the UUID of the event being processed in the `causation_id`
+  of any emitted events. This replaces the old behaviour of storing id of the
+  event being processed in a `_driven_by_event_id` attribute in the emitted
+  event's body.
+
+### Added
+- Reactors store the correlation id of the event being processed in the
+  `correlation_id` of any emitted events.
+- Added index on the `events` table for `correlation_id` and `causation_id`
+  columns.
+
 ## [0.3.0] - 2017-6-16
 ### Changed
 - The event store persists the event `correlation_id` and `causation_id`.
   To facilitate this `correlation_id` and `causation_id` columns have been
   added to the `events` table and the `write_events` function has been