update README, fixes #22

README.md

@@ -37,7 +37,15 @@ Kallithea is *"a free software source code management system supporting two lead
 
 ### Setup Requirements
 
-For full functionality, Kallithea requires git to be installed. This module can optionally git as well, but this requires the `puppetlabs/git` module.
+For full functionality, Kallithea requires git to be installed. This module can
+optionally install git as well, but this requires the `puppetlabs/git` module.
+
+** *INCOMPATIBILITY WITH PUPPET 4.0 and 4.1* **: Due to a [known
+bug](https://tickets.puppetlabs.com/browse/MODULES-2867) in
+[`puppetlabs/stdlib`](https://forge.puppetlabs.com/puppetlabs/stdlib), the
+Puppet versions 4.0 and 4.1 are not supported. See also
+[here](https://github.com/rauchrob/puppet-kallithea/issues/22) for more
+information.
 
 ### Beginning with kallithea