TEST: detect_vertebral_levels: added test
TEST: detect_vertebral_levels: added test

Former-commit-id: 3758523dbbb64251c3694cee1d7d15cf6e9f5471 [formerly 22579602b722a33748ac2bf4041f6560b3b79cb0]
Former-commit-id: 771dc9a210feea0be9a31fcc77890f4b2c864380
Former-commit-id: a8b6c9fd014004f92a9a186b77464a44d40383e6
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox