Monte Carlo numerical multiple integration with simplex

Monte Carlo numerical integration for integrals of any size.

Monte Carlo numerical integration for integral of any size.
Inputs:
- f : handle to the (vectorial column) function to integrate
- in : N-by-dim matrix containing the sample points (N is the number of samples, dim is the number of variables)
- lo : lower bounds of integration
- hi : upper bounds of integration
- useSimplex : if the points were sampled from the simplex

Outputs:
- out : (vector column) result