Added update section to readme

Author: mblaschke

README.md

@@ -33,6 +33,7 @@ Use can use my [Vagrant Development VM](https://github.com/mblaschke/vagrant-dev
 ## Table of contents
 
 - [Installation and requirements](/documentation/INSTALL.md)
+- [Updating docker boilerplate](/documentation/UPDATE.md)
 - [Docker Quickstart](/documentation/DOCKER-QUICKSTART.md)
 - [Run your project](/documentation/DOCKER-STARTUP.md)
 - [Container detail info](/documentation/DOCKER-INFO.md)

documentation/UPDATE.md

@@ -0,0 +1,14 @@
+[<-- Back to main section](../README.md)
+
+# Update
+
+# Update to 3.4.x
+As `PHP_UID` was replaced with `EFFECTIVE_UID` and `PHP_GID` was replaced with `EFFECTIVE_GID` you
+have to rebuild all containers with this variables: `main` and `web`
+
+```bash
+docker-compose stop
+docker-compose rm --force main web
+docker-compose build --no-cache main web
+docker-compose up
+```