non-default curvature files improperly named

[binarybottle]

Revised code gives proper names to non-default (gaussian, max, min) curvature output files in surface_shaps.py:

    basename = os.path.splitext(os.path.basename(surface_file))[0]
    stem = os.path.join(os.getcwd(), basename)
    mean_curvature_file = stem + '.mean_curvature.vtk'
    if method in [0, 1]:
        gauss_curvature_file = stem + '.gauss_curvature.vtk'
        args.extend(['-g', gauss_curvature_file])
    if method == 0:
        max_curvature_file = stem + '.max_curvature.vtk'
        min_curvature_file = stem + '.min_curvature.vtk'
        min_curvature_vector_file = stem + '.min_curvature.txt'
        args.extend(['-x', max_curvature_file,
                     '-i', min_curvature_file,
                     '-d', min_curvature_vector_file])