Added installation section in PageRevision readme

PageRevision.md

@@ -4,6 +4,15 @@ PageRevisionMacro
 Show the current page name and revision number on a [MoinMoin][moin] wiki page
 
 
+Installation
+------------
+
+To install the macro, copy the file `PageRevision.py` into the
+`/path_to_wiki_instance/data/plugin/macro` directory. This method should
+survive a MoinMoin or Python upgrade. Make shure, that the file has
+the right ownership and permissions.
+
+
 Usage on a MoinMoin wiki page
 -----------------------------