Delta and Gamma computation one step in the future
Otherwise one can do the following,
Instead of computing a BinomialTree at (K,T,S,r,N,sigma)
we do so
 for a Binomial tree (K,(N+2)T/N,S,r,N+2,sigma) for which
we find delta and gamma for point (2,1)

For Vega we find C for sigma+Dsigma and sigma-Dsigma
and then C(sigma+Dsigma) - C(sigma-Dsigma) / 2Dsigma is vega
with Dsigma = 0.001 Sigma

and for rho do the same for r...
