fix changelog; add entry

CHANGELOG.md

@@ -5,11 +5,12 @@ All PRs to the Wasmer repository must add to this file.
 Blocks of changes will separated by version increments.
 
 ## **[Unreleased]**
+- [#399](https://github.com/wasmerio/wasmer/pull/399) Add example of using a plugin extended from WASI
+- [#397](https://github.com/wasmerio/wasmer/pull/397) Fix WASI fs abstraction to work on Windows
+- [#390](https://github.com/wasmerio/wasmer/pull/390) Pin released wapm version and add it as a git submodule
 
 ## 0.4.0 - 2018-04-23
 
-- [#397](https://github.com/wasmerio/wasmer/pull/397) Fix WASI fs abstraction to work on Windows
-- [#390](https://github.com/wasmerio/wasmer/pull/390) Pin released wapm version and add it as a git submodule
 - [#383](https://github.com/wasmerio/wasmer/pull/383) Hook up wasi exit code to wasmer cli.
 - [#382](https://github.com/wasmerio/wasmer/pull/382) Improve error message on `--backend` flag to only suggest currently enabled backends
 - [#381](https://github.com/wasmerio/wasmer/pull/381) Allow retrieving propagated user errors.