REF: removed use_continuous_labels=0 feature from sct_straighten_spinalcord. Fixed #577
REF: removed use_continuous_labels=0 feature from sct_straighten_spinalcord. Fixed #577

Former-commit-id: a5b959c107913d6a950591366cace4d8da731dd7 [formerly e46a14e17e96128bca43a173ca3f214645a8218d]
Former-commit-id: 475e1d3910394406a12ae838a6702f670d14154f
Former-commit-id: a34539dda32a7700b31345e588ab8a8cb571215e
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox