BUG: RidgeExtractor set xstep to 3-vector regardless of image dim
BUG: RidgeExtractor set xstep to 3-vector regardless of image dim

cdeepakroy/TubeTK,sumedhasingla/TubeTK,aylward/ITKTubeTK,KitwareMedical/TubeTK,matthieuheitz/TubeTK,aylward/ITKTubeTK,aylward/ITKTubeTK,KitwareMedical/TubeTK,cdeepakroy/TubeTK,sumedhasingla/TubeTK,KitwareMedical/ITKTubeTK,cdeepakroy/TubeTK,thewtex/TubeTK,sumedhasingla/TubeTK,LucasGandel/TubeTK,cdeepakroy/TubeTK,thewtex/TubeTK,matthieuheitz/TubeTK,KitwareMedical/ITKTubeTK,KitwareMedical/TubeTK,matthieuheitz/TubeTK,LucasGandel/TubeTK,thewtex/TubeTK,aylward/ITKTubeTK,LucasGandel/TubeTK,matthieuheitz/TubeTK,KitwareMedical/TubeTK,sumedhasingla/TubeTK,KitwareMedical/ITKTubeTK,LucasGandel/TubeTK,thewtex/TubeTK,KitwareMedical/ITKTubeTK