got rid of a bit of useless code related to infile/outfile. changed the output so that if we specify a destination file, that name gets used, otherwise the source filename is used (or - for stdin)
got rid of a bit of useless code related to infile/outfile. changed the output so that if we specify a destination file, that name gets used, otherwise the source filename is used (or - for stdin)

guppy/ddsum