-currently: trying to get spherical polygon surface area calculation working
-added a new unit test (surface area calculation) for a simple case of a single spherical triangle on the unit sphere
-increased stringency of test_spherical_triangle_sum_inner_angles test
-adjusted self.spherical_triangle_coordinate_array test coords to avoid the 'co-linear' case I had been using for some tests
-added a unit test for inner angle summation of a spherical polygon with >3 vertices