Replace step_length_cgm() with a direct call to step_length_positive_definite().
Use the infinity norm in vanilla_cgm(). Simplify the loop in vanilla_cgm().
Clean up the loop in the vanilla CGM. Make the roundoff error modification from the PCGM in the vanilla CGM.
Fix function name in vanilla_cgm.m. Remove unused vector in vanilla_cgm().
Move conjugate_gradient_method.m to vanilla_cgm.m. Implement conjugate_gradient_method() in terms of the preconditioned CGM. Add the slow, simple preconditioned CGM as simple_preconditioned_cgm().