ENH: Bump ExternalInsight version.

Bump ITK to the latest version in Slicer.  This is the commit
on the release branch that will likely be ITK v4.4.1.

Closes issue #30.

Change-Id: I3186240cc8c500009f7c798f6f135460f76e2a2c
ENH: Bump External_VTK to the current Slicer version.

Closes issue #30.

Change-Id: I9914e95da58e3e566710f879dbaf5bd54553d984
Merge topic 'ITKVTKBump'

5b1cbbc ENH: Bump External_VTK to the current Slicer version.
c61af0f ENH: Bump ExternalInsight version.
WIP: UseTubeMacro

Change-Id: I1e7d41f2dde22e45608dc8465a11d6d7f97bc60e