Refactored the sct_utils file.
Refactored the sct_utils file.

Removed old code and comments. And comply to pep8 style guide.


Former-commit-id: 65086179f45b4283eca323bddc400e60f90b60db
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox