Change cuts on z_best to probabilistic cuts on P(z)

[deapplegate]

WtG code cuts on z_best z_cluster + delta < z_best < 1.25. Change to make probabalistic cut using P(z), at least on low redshift cluster end.

At line https://github.com/deapplegate/Clusters/blob/master/pzmassfitter/maxlike_masses.py#L138A