OS X build fixes
Tweak OS X compilation
Added a curvature parameter to region_3d

Added a curvature parameter to region_3d

Rebase test

Update region_3d.h

Update region_3d.h

Update region_3d.h
Merge pull request #658 from eile/master

OS X build fixes
Merge pull request #653 from EduFdez/master

Added a curvature parameter to region_3d. This parameter characterizes the mean curvature of the 3D region.