Update README.md

Author: NikolayS

README.md

@@ -4,6 +4,8 @@ The missing set of useful tools for Postgres DBA.
 
 ## Requirements
 
+You need to have psql version 10, but the Postgres server itself can be older – most tools work with it (if not, it's mentioned in description of such a tool).
+
 ## Installation
 Clone, go to the directory and run psql (version 10 is required):
 ```bash