This feature is now available for any installable revision of a repository using the new "Export this revision" option in the Repository actions menu in the browser. It is also available via the Tool Shed API using a command like the following:
export.py --url http://testtoolshed.g2.bx.psu.edu --name chemicaltoolbox --owner bgruening --revision 4133dbf7ff4d --export_repository_dependencies True --download_dir /tmp