include instruction to install version 0.4.0 in installation instructions

docs/installation_instructions.rst

@@ -66,11 +66,11 @@ Getting the installation script
 -------------------------------
 
 On your **provisioning machine**, clone the OpenAppStack git repository
-and checkout the latest tagged version (currently ``0.3.1``):
+and checkout the latest tagged version (currently ``0.4.0``):
 
 ::
 
-    $ git clone -b 0.3.1 https://open.greenhost.net/openappstack/openappstack.git
+    $ git clone -b 0.4.0 https://open.greenhost.net/openappstack/openappstack.git
     $ cd openappstack
 
 .. note::