Better bound for Taylor Model product

[ulinares]

Playing around with the implementation of the product of Taylor Models given in [1],
I found that his implementation gives a better bound for the resulting Taylor Model, eg, the TaylorModel1 product for f(x) = sin(x), g(x)=cos(x) + x^3, gives the following results

Green boxes correspond to the case where the diameter of the bound given by the current implementation is equal
to the diameter of the bound given by the implementation in [1].
Red boxes correspond to the case where the diameter of the bound given by [1] is less than the bound given by the
current implementation.

What do you think about this @lbenet?

[1] A Taylor model toolbox for solving ODEs implemented in MATLAB/INTLAB, Floarian Bünger

[lbenet]

Excellent! Can you make a PR?

[lbenet]

I think it is worth the extra evaluation and the intersection...