create the atom feed with the issues in the correct order

issues/tools/atom.sh

@@ -22,7 +22,7 @@ cat <<EOF
   <updated>${date_updated}</updated>
 EOF
 
-for page in ../public/issue-*.html ; do
+for page in $(ls -t ../public/issue-*.html) ; do
     issue=$(echo $page | grep -oE "issue\-[0-9]+")
     title=$(echo $issue | awk -F '-' '{ print "Issue #"$NF }')
     . ./$issue/metadata.sh