STYLE: update VTK to include vtkChartXY improvements
Prerequisite: https://github.com/Slicer/VTK/pull/19
ref: https://github.com/Slicer/Slicer/pull/994#issuecomment-410730215
git shortlog origin/slicer-v9.0.0-2018-04-17-10e8cdc..slicer-v9.0.0-2018-04-17-10e8cdc
Davide Punzo (3):
ENH: added single click selection in chartXY
BUG: fix for selection vtkChart test failing
STYLE: fix formatting vtkChartXY