Update README.md

Author: huksley

README.md

@@ -21,7 +21,7 @@ Allows to send syslog messages with TCP or UDP formatted as plain text (classic)
   * Protocol: use tcp or udp
   * Host: Hostname with syslog 
   * Port: Port for syslog, usually 514
-  * Format: Specify one of plain, structured, full, cef or custom:<ClassName> (see below for explanation on values)
+  * Format: Specify one of plain, structured, full, cef or custom:FQCN (see below for explanation on values)
 
 ## Supported formats
 
@@ -41,6 +41,10 @@ Common event format aka HP ArcSight format. This is Work in progress as I don`t
 
 A variation of structured format except full message is added.
 
+### custom:FQCN
+
+Specify your implementation of com.wizecore.graylog2.plugin.MessageSender interface. 
+
 ## Links
 
   * https://tools.ietf.org/html/rfc5424