Update changelog

Author: sagikazarmark

CHANGELOG.md

@@ -6,6 +6,11 @@
 
 - Client factories for Buzz.
 
+### Changed
+
+- **[BC] PluginClientFactory returns an instance of `Http\Client\Common\PluginClient`** (see [php-http/client-common#14](https://github.com/php-http/client-common/pull/14))
+- Plugins are loaded from their new packages, fall back to `php-http/plugins` if necessary
+
 
 ## 1.0.0 - 2016-03-04