Added another adaptive step-size algorithm. This is le Cun's 1993 one based upon an online computatino of the max eigenvalue of the Hessian. Works quite well. Unfortunately, the version of the algorithm meant for rescaled parameter spaces (when the update is multiplied by some matrix, like the inverse of the Hessian or soemthing) doesn't seem to work at all. I'll try it some more, but for now it is staying out of the repo.