If there is only 1 core, use 1, not 0.5 cores.
Truncate the number of threads if uneven number
Merge pull request #22 from johandahlberg/minimum_one_core

A even number of cores should always be offered to make
fixed missing semi-colon
Merge pull request #23 from b97pla/sisyphus-dev

fixed missing semi-colon
Merge branch 'sisyphus-dev' of https://github.com/Molmed/sisyphus into feature/miseq_upload_as_argument