[Core] Added changelog for 0.2.0 (#200)

* [Core] Added changelog for 0.2.0

* Updated with AwsClientFactory

Author: Nyholm

CHANGELOG.md

@@ -0,0 +1,17 @@
+# Change Log
+
+## 0.2.0
+
+### Added
+
+- Class `AsuncAws\Core\Credentials\NullProvider`
+- Methods `AwsClient::cloudFormation()`, `AwsClient::lambda()`, `AwsClient::sns()`
+
+### Changed
+
+- Removed `AwsClient` and replaced it with `AwsClientFactory`
+- Class `AsuncAws\Core\Signers\Request` is marked as internal
+
+## 0.1.0
+
+First version