Update change log.

Author: paurkedal

CHANGES.md

@@ -1,5 +1,13 @@
 # Changes
 
+## v0.4.0
+
+- Switched to internal regexp parser.
+- Added syntax extension for `tyre` (Gabriel Radanne).
+- Fixed type of captures under alternatives for `%pcre`.
+- Improved error reporting with locations.
+- The PPX now declares its runtime libraries.
+
 ## v0.3.2 - 2018-03-01
 
 - Prepare for re 1.7.2.