explain why the plackup server throws warnings on older perls

Author: wchristian

README.pod

@@ -24,3 +24,7 @@ which will be loaded on top of the existing config file.
 
 This will use the API server at C<localhost:5000> and sets the port of the front-end to 5001.
 The process will watch changes in the C</lib> directory.
+
+=head1 COMPATIBILITY NOTES
+
+On Win32 (and possibly also on other platforms) when using Perl < 5.12, the server started with plackup will generate warnings relating to date parsing. These are caused by Plack due to a bug in the gmtime implementation and can be removed by upgrading to Perl 5.12.