added Gruntfile
moved center of mass of tetrahedra in demos, since they looked a bit buggy. Thanks to @dirkk0
Fixed face vertices order of ConvexPolyhedra in demos, Cylinder and Box. Now they all should be CCW (bunny still not fixed though). Auto-construction of normals by ConvexPolyhedron. Warning from ConvexPolyhedron constructor if non-CCW order was found.