add BytesIO/bytes support, dst_format param and delegate format

conversion to optimize_xxx methods

Author: cking100

CHANGELOG.md

@@ -11,6 +11,7 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
 
 - Add support for custom number of retries and user-agent in save_large_file (#278)
 - Enhance save_large_file log level (#279)
+- Extend image optimization to support in-memory streams(BytesIO/bytes) and dst_format param (#289)
 
 ### Fixed