Bump VTK package version.
Bump VTK package version.

vistrails/packages/vtk/identifiers.py:
  - bump version to 0.9.4

VisTrails/VisTrails,hjanime/VisTrails,hjanime/VisTrails,hjanime/VisTrails,celiafish/VisTrails,minesense/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,minesense/VisTrails,hjanime/VisTrails,minesense/VisTrails,VisTrails/VisTrails,Nikea/VisTrails,VisTrails/VisTrails,Nikea/VisTrails,celiafish/VisTrails,Nikea/VisTrails,minesense/VisTrails,celiafish/VisTrails,minesense/VisTrails,celiafish/VisTrails,hjanime/VisTrails,VisTrails/VisTrails