add some comments for the fastq driver

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
improve manual of spate

Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>
add support for formats .fasta, .fasta.gz, .fa, .fa.gz

Link: https://github.com/GeneAssembly/biosal/issues/247
Signed-off-by: Sébastien Boisvert <boisvert@anl.gov>