added per_event_bfs_and_n_effectives method
Most recent change to MinimumEffectiveSamplesLikelihood broke this line of the function that fills n_effective because we changed the name of the function because it compute variances as well. So I added a function with the appropriate name that just called the per_event_bfs_and_n_effectives_and_variances and just returns the per event bfs and n_effectives. I did not put in a docstring because it simply just calls another function.