altered formulation for gradients of slope in the anisodiffusion flag in diffusion.f95. However, I am not sure it is correct quite yet. I want to carefully evaluate the indices used in both h and the grid spacing.
commented out and added thoughts to a bunch of places where there seems to be a hardwired east-west periodic boundary condition. I think the original intent of the code was for global modeling and hence the fact that it is hardwired,  but I am not sure if another boundary condition is needed to replace that one. That is a question to yet be answered.
fixed anisodiffusion calculation for grdx and grdy calculation