Fix comment in get_atomset.sh

util/get_atomset.sh

 #!/bin/bash
 # get_atomset: extract atomset from a Qbox sample
 #
-# use: get_atomset sample.xml
+# use: get_atomset.sh sample.xml
 #
 nlines=$(grep /atomset -m 1 -n $1 | cut -f1 -d: - )
 head -$nlines $1