Resolved issue #52 logic was added to find an upper or lower vertex on the wavefront by checking that the change in the propagation direction of the wavefront had changed and in which direction.
The refraction_munk_range test was modified to include a BOOST_CHECK_EQUAL statement that verifies that the upper and lower vertex for point on the wavefront had both been incremented by one for each cycle.
Changed check of offsets in spreading_hybrid_gaussian to be less then zero. Previous check was incorrect.
Various small cleanup to the ordering of member variables of the wavefront.