Fix typo in readme

Author: joelwurtz

README.md

@@ -69,7 +69,7 @@ Versioning
 Docker PHP does not follow the classic [semver versioning](http://semver.org/), but follow the Docker Remote API
 versioning starting at the v1.21, the master branch will follow the next major release on the Docker Remote API.
 
-Changes on the core of this library not directly to the API, will be merged back to previous versions
+Changes on the core of this library not related to the API, will be merged back to previous versions
 on a best effort basis.
 
 Credits