Emille's development: new file - sequential_ABC.py

File sequential_ABC.py: Implements sequential ABC algorithm translated from Jessi's R code using a 7 number summary statistics based on quantiles.

File NCountSimul.py:
included function choose_par, which selects proper parameter values for om, ol and w given a prior distribution;
included function set_distances, which calculates the distance between the fiducial data and a model given by its cosmological parameters;
included function choose_surv_par, which selects a required number of cosmological parameters values passing summary statistics requirements.