Add a note in README about the origin of pg_arman

Michael Paquier · Michael Paquier · commit 4d586dda9cec · 2014-01-27T12:19:00.000+09:00
diff --git a/README b/README
@@ -82,4 +82,5 @@ License
 -------
 
 pg_arman can be distributed under the PostgreSQL license. See COPYRIGHT
-file for more information.
+file for more information. pg_arman is a fork of the existing project
+pg_rman, initially created and maintained by NTT and Itagaki Takahiro.
