COMP: Add missing vector header include.
COMP: Add missing vector header include.

Without this include, a compilation error results on some compilers.

InsightSoftwareConsortium/ITKMinimalPathExtraction,InsightSoftwareConsortium/ITKMinimalPathExtraction,KitwareMedical/ITKMinimalPathExtraction,thewtex/ITKMinimalPathExtraction,InsightSoftwareConsortium/ITKMinimalPathExtraction,KitwareMedical/ITKMinimalPathExtraction,thewtex/ITKMinimalPathExtraction,thewtex/ITKMinimalPathExtraction