fix kmers length issues

Reviewed-by: Sebastien Boisvert <sebastien.boisvert.3@ulaval.ca>
Signed-off-by: Maxime Déraspe <maximilien1er@gmail.com>
Merge branch 'fixkmerlen' of https://github.com/Zorino/ray.git

Merge Surveyor work by Maxime Déraspe
Surveyor: add documentation for reading a sequence file

Signed-off-by: Sébastien Boisvert <sebastien.boisvert.3@ulaval.ca>