Add an usage example for parallel_parse.sh .

parallel_parse.sh

@@ -4,6 +4,12 @@ usage() {
   echo "  find [...] -print0 | $0 \\"
   echo "    parallelism state_dir out_file command [arg1 [...]]"
   echo "Reads filenames to process from stdin, null-delimited."
+  echo
+  echo "Example: parsing any number of log files with up to 4"
+  echo "processes in parallel with locally built pypy:"
+  echo "  $ mkdir state"
+  echo "  $ $0 4 state out.tml /usr/local/bin/pypy \\"
+  echo "    bin/apachedex --period week"
 }
 
 if [ $1 = '-h' -o $1 = '--help' ]; then