sftp in backup_zh-4.2.0

- old
+ new

@@ -6,9 +6,10 @@
     server.password   = "my_password"
     server.ip         = "123.45.678.90"
     server.port       = 22
     server.path       = "~/backups/"
     server.keep       = 5
+    # server.keep       = 1.year.ago # Remove all backups older than 1 year.
 
     # Additional options for the SSH connection.
     # server.ssh_options = {}
   end