Add 1.9.0 changelog entries

CHANGELOG.md

@@ -1,8 +1,17 @@
 # CHANGELOG
 
-## Unreleased
-
-- ...
+## 1.9.0 (2018-05-03)
+
+- Fixed undefined variable (#588)
+- Fix for exceptions throwing exceptions when setting event id (#587)
+- Fix monolog handler not accepting Throwable (#586)
+- Add `excluded_exceptions` option to exclude exceptions and their extending exceptions (#583)
+- Fix `HTTP_X_FORWARDED_PROTO` header detection (#578)
+- Fix sending events async in PHP 5 (#576)
+- Avoid double reporting due to `ErrorException`s (#574)
+- Make it possible to overwrite serializer message limit of 1024 (#559)
+- Allow request data to be nested up to 5 levels deep (#554)
+- Update serializer to handle UTF-8 characters correctly (#553)
 
 ## 1.8.4 (2018-03-20)