Advanced techniques for numerical minimization

Begin by copying all of your ``.m'' files from ``$\sim$/A2a'' into a new directory ``$\sim$/A3'' and proceed to work there.

In this problem, we implement line minimization, preconditioning, and conjugate gradients. To verify the convergence properties of the various techniques, each function will return, as an optional second argument, the list of energies at each stage of the minimization. We begin by adding this capability to sd().