Funz algorithm: GradientDescent

GradientDescent first-order local optimization algorithm
http://en.wikipedia.org/wiki/Gradient_descent
author: Yann Richet
tags: Optimization
options: nmax=10; delta=0.1; epsilon=0.01; target=0.0
input: x=list(min=0,max=1)
output: y=0.99