senderscore: fix doc

plugins/senderscore/senderscore

@@ -1,5 +1,13 @@
 #!/usr/bin/python
-
+#
+# Here's a plugin which lets you monitor your senderscore.org reputation. For
+# people sending a large amount of email - this might be useful.
+#  
+# Config env var used:
+# [senderscore]
+#  env.senderscore_check_ip xxx.yyy.zzz.ttt
+#
+
 import socket
 import sys
 import os