Allow sxiv_workaround_hook to Work if Command Contains "sxiv "

Currently the command in the `rifle.conf` must start with "sxiv " for all images in the directory to be opened. My sxiv command for opening images, however, does not start with sxiv and calls another script first. Is there a reason that the command should start with "sxiv " (or "feh ") as opposed to just containing it?