Travis build matrix to do parallel builds for make and CMake; CUDA-less
and CUDA-ful.  Move bits of functionality into scripts under scripts/travis
for readability. Only generate CUDA compute_50 for perfomance.
Merge pull request #943 from jeffdonahue/parallel-travis-builds

add Travis build matrix to do parallel builds for (make, CMake) x (with CUDA, without CUDA)