COMP: Fix External_VTK CMake warning
ENH: Sync external project versions and arguments with Slicer
ADD: Test for TubeGraphToImage

     Added MIDAS keys + CMakeLists.txt for testing the TubeTK
     TubeGraphToImage Application.

     Commented out unused code.
ADD: Missing MIDAS keys for TubeGraphToImage testing.
ENH: New method for shrinking an image using a max function for summary
ENH: Updated test baseline for itktubeShrinkUsingMaxImageFilter
COMP: Remove USE_SIMPLEITK option
Merge pull request #94 from aylward/ShrinkUsingMax

ENH: New method for shrinking an image using a max function for summary
Merge pull request #92 from jamiesnape/UpdateDependencies

ENH: Sync external project versions and arguments with Slicer
Merge pull request #93 from rkwitt/Additional-Tests

ADD: Test for TubeGraphToImage
BUG: Create Python virtualenv at configure time. #95.

The virtualenv needs to available to install the tubetk packages for testing.