update changelog

Author: chriskapp

CHANGELOG.md

@@ -1,5 +1,13 @@
 # Changelog
 
+## 0.9.0 - WIP
+
+### Changes
+- PowerPoint2007 Writer : Write percentage values with a trailing percent sign instead of formatted as 1000th of a percent to comply with the standard - @k42b3 GH-307
+
+### Features
+- PowerPoint2007 Writer : Implemented XSD validation test case according to the ECMA/ISO standard - @k42b3 GH-307
+
 ## 0.8.0 - 2017-04-03
 
 ### Bugfix