Tabulation at the ends #28
Description
Currently, our tabulate_model function starts at the LHS or RHS of the model with a point and takes fixed steps reporting the value at each point unless it meets a breakpoint (in which case it returns two values, one from "above" and one from "below") and starts the next step from there. What it does not do is add a point at the far end. We should probably include a point at the surface (if we come from the center of the Earth) or the center of the Earth (if we come from the surface)... but need to check this is what's expected from Mineos and TauPy. Also need to document and test this behaviour.