Good-Turing probabilities estimator

[kahaaga]

Describe the feature you'd like to have

At some point, I had implemented the Good-Turing probabilities estimator. I'm not sure if it disappeared from the list of estimators, or if I forgot to push a PR for it. In any case: we should include it.

Cite scientific papers related to the feature/algorithm

This paper, for example, uses a variant of it that we should implement.
This reference is also useful

[Datseris]

I didn't delete any branches, and the only other branch that is pushed is about Pal differential entropy estimator (2690eac) . Unfortunately you likely forgot to push :( I hope you can find the code!

[kahaaga]

:( Well well, no worries. I had a quite prolific period of implementing new things just before we started reorganising the package, so there's a bit of a backlog on things that should be included here. I'm sure I can dig up the code from somewhere :D