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