option to include everything in atom feed

Fixed missing newlines in help message and made it so that setting the -m flag
to 0 incudes all files in the atom feed. Also madde this behaviur the default

rivet.1

@@ -51,6 +51,7 @@ Set the description of the atom feed to
 .IP "\-n number"
 Set the maximum number of elements in the atom feed to 
 .I number
+setting it to '0' includes all files
 .IP \-v
 verbose option, sets -x and prints every command as it runs
 .IP \-h