-* Improved documentation.
-* Upgrade bundled ion-c library.
-* Fix gh-issue #5: ion\Timestamp crashes with string timezones.
-* Add ion\Exception.
-* Refactor (un)serialization facilities:
- * Removed ion\Reader\Options class and moved the options to the ion\Reader constructor.
- * Removed ion\Writer\Options class and moved the options to the ion\Writer constructor.
- * Renamed ion\Serializer\PHP to ion\Serializer\Serializer.
- * Renamed ion\Unserializer\PHP to ion\Unserializer\Unserializer.
- * Changed ion\Serializer::serialize(mixed $data) to
- ion\Serializer::serialize(mixed $data, ion\Writer|array|null $writer = null).
- * Changed ion\Unserializer::unserialize(string|resource $data) to
- ion\Unserializer::unserialize(ion\Reader|string|resource $data)
-* Add support for custom (un)serializers.