more docs for merchant script

scripts/merchant/merchant.readme

@@ -22,3 +22,15 @@ however, need to manually adjust your "gap limit".
 
 In order to use this script, first edit and rename
 merchant.conf.template to merchant.conf
+
+to launch it, type:
+> python merchant.py
+
+In another terminal, you may send a request from the command line (it
+will send the request to the running daemon via http). For example,
+here is a request for 0.1 bitcoins, that requires two confirmations,
+and expires in 120 minutes:
+
+> python merchant.py request 0.1 2 120
+
+