update README.md correct versions to 4.*

Author: TomHAnderson

README.md

@@ -10,9 +10,9 @@ and [DoctrineMongoODMModule](https://github.com/doctrine/DoctrineMongoODMModule)
 
 ## Versions
 
-The most recent versions of this module are on the **2.0.x** branch.
-There is a 2.1.x branch and release but this is reserved for future integrations with unreleased Doctrine projects.
-If you are including this module in your composer file then use a **2.0.x** release.
+The most recent versions of this module are on the **4.0.x** branch.
+There is a 4.1.x branch and release but this is reserved for future integrations with unreleased Doctrine projects.
+If you are including this module in your composer file then use a **4.0.x** release.
 
 ## Documentation