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

3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox,3324fr/spinalcordtoolbox