docs: update CHANGELOG for version v0.3.1

CHANGELOG.md

@@ -4,6 +4,11 @@ All notable changes to this project are documented in this file.
 
 **THIS LIBRARY IS STILL IN ALPHA AND THERE ARE NO GUARANTEES REGARDING API STABILITY YET**
 
+## [v0.3.1] - 2019-10-09
+- Fix HTML characters escaping in struct field names.
+- Add examples for Marshal, MarshalTo and Encoder's Encode.
+- Refactor string encoding to be compliant with `encoding/json`.
+
 ## [v0.3.0] - 2019-09-23
 - Add global functions `Marshal`, `MarshalTo` and `Register`.
 - Update `README.md`: usage, examples and benchmarks.
@@ -24,6 +29,7 @@ All notable changes to this project are documented in this file.
 ## [v0.1.0] - 2019-08-30
 Initial realease.
 
+[v0.3.1]: https://github.com/wI2L/jettison/compare/v0.3.0...v0.3.1
 [v0.3.0]: https://github.com/wI2L/jettison/compare/v0.2.1...v0.3.0
 [v0.2.1]: https://github.com/wI2L/jettison/compare/v0.2.0...v0.2.1
 [v0.2.0]: https://github.com/wI2L/jettison/compare/0.1.0...v0.2.0