Small update to supervoxel clustering tutorial
apps cmake wasn't cascading when deps wasn't found.
Fix for building cloud editor in Mac

related to #364
CLang won't support OpenMP in the near future (http://clang-omp.github.io/)
Merge pull request #379 from nizar-sallem/clang_openmp

CLang won't support OpenMP in the near future
Merge pull request #376 from fran6co/fix-cmake-apps

apps cmake wasn't cascading when deps weren't found.
Merge pull request #378 from fran6co/patch-4

Fix for building cloud editor in Mac
Merge pull request #375 from jpapon/supervoxel_tutorial_fix

Small update to supervoxel clustering tutorial
refactored getTotalSystemMemory a bit, just to make it easy to extend it
_SC_AVPHYS_PAGES doesn't exist in Mac OS X
Merge pull request #377 from fran6co/patch-2

_SC_AVPHYS_PAGES doesn't exist in Mac OS X
Don't export compiler flags to user code

We should only export needed definitions, not compiler flags as this
breaks user code (see #371 for an example).
Remove superfluous flags from tutorials
Really only set CMAKE_CXX_FLAGS if empty on GCC
Revert "Really only set CMAKE_CXX_FLAGS if empty on GCC"

This reverts commit 20c95ddcad13bce5b72ca6bc84368b3c6473a8e4.