build RTK on ubuntu 16.04

RTK-1.4.0

InsightToolkit-4.12.2

cmake -D ITK_DIR=/home/peng/projects/CT/InsightToolkit-4.12.2/build ..

cmake -D ITK_DIR=/home/peng/projects/CT/InsightToolkit-4.12.2/debug -D CMAKE_BUILD_TYPE=Debug -D RTK_USE_CUDA=ON ./RTK-1.4.0/

note : 

it is needed to for test code

#define USE_CUDA