add note about temporary directories
add note about temporary directories


Former-commit-id: a4811f2fcc107e716fcddf9d9cd727ed8cc01e0d
neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox,neuropoly/spinalcordtoolbox