v0.0.3: 13 quantile (#17)

In this release, we add the Sobol indices (first, total and second order) for the Martinez (pearson coefficient), Jansen and Saltelli methods.
We also add quantiles method (based on RM algorithm) (it is still a work in progress).

We integrate a fault-tolerance property by adding two methods: load_from_state() and save_state() to the abstract class IterativeStatistics.