Update CHANGELOG for v4.0.0

RyanZim · RyanZim · commit 74d33dd27ff9 · 2017-05-09T10:32:03.000-04:00
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,8 @@
+4.0.0 / 2017-05-09
+==================
+
+- **BREAKING:** Upgrade postcss to v6.x
+
 3.2.0 / 2017-04-21
 ==================
 
