Updates version and documents changes

Consolidates subsequent commit version increases into one release.
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 8567408..906ad3f 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,14 @@
+## 0.13.3
+
+* Adds support for shadow host selectors `:host()` and `:host-context()`.
+* Adds support for shadow-piercing descendant combinator `>>>` and its alias
+  `/deep/` for backwards compatibility.
+* Adds support for non-functional IE filter properties (i.e. `filter: FlipH`)
+* Fixes emitted CSS for '@page' directive when body includes declarations and
+  page-margin boxes.
+* Exports `Message` from `parser.dart` so its no longer necessary to import
+  `src/messages.dart` to use the parser API.
+
 ## 0.13.2+2
 
 * Fix static warnings.
diff --git a/pubspec.yaml b/pubspec.yaml
index 8ed29b6..f1cac20 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: csslib
-version: 0.13.6
+version: 0.13.3
 author: Dart Team <misc@dartlang.org>
 description: A library for parsing CSS.
 homepage: https://github.com/dart-lang/csslib