ENH: Bump External_VTK to the current Slicer version.
ENH: Bump External_VTK to the current Slicer version.

Closes issue #30.

Change-Id: I9914e95da58e3e566710f879dbaf5bd54553d984

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