Remove Extract seed step

Extract seed step was used for the SegmentTubeSeeds CLI that was removed.
Consequently also remove this step.
Merge pull request #25 from vovythevov/Workflow-FixSegmentTubeSeedsDeletion

Remove Extract seed step
Bump TubeTK for release
Use our own fork of Slicer for VesselView
Update Applications folder after Slicer update
Bump TubeTK for vtk6 support
AMEND WITH SLICER UPDATE
AMEND WITH SLICER FIX
WIP