Fix for seg fault on Linux exit.
Enable alpha testing for models.
Somewhat inefficient take on allowing blendshapes coefficients to apply
multiple blendshapes.
More efficient (though perhaps overkill) blendshape mapping.
Merge branch 'master' of https://github.com/worklist/hifi
Merge pull request #1351 from ey6es/master

Fix for segfault on Linux exit; enable alpha testing for models; allow coefficients to apply multiple blendshapes.
Merge branch 'master' of https://github.com/worklist/hifi into metavoxels