changed to use system VTK paths

Neither the VTK include paths or the VTK libraries listed currently are valid on Fedora.

If you use CMake to detect these values, they'll be right on any system with valid VTK.

Example build break: http://csc.mcs.sdsmt.edu/jenkins/job/ros-indigo-pointcloud-tools_binaryrpm_heisenbug_x86_64/2/console

Thanks,

--scott