Add argument to only evaluate single-speaker regions

[thequilo]

Adresses #62. The name is still up for discussion.

[boeddeker]

@TCord Could you add a sentence, where the user should be careful? Or was that only relevant, if you want to calculate the overlap only DER?

[boeddeker]

I vote for--regions [all|single|overlap|nonoverlap] instead of adding a new option that is not used in any existing framework.
It is already used in spyder and works for md-eval, dscore, pyannote and spyder.

[thequilo]

I also like --regions, but md-eval only supports --regions [all|nooverlap]. Also, should we name it --score-regions?

[boeddeker]

I also like --regions, .... Also, should we name it --score-regions?

Hmm. My motivation was to use the same name as others.

but md-eval only supports --regions [all|nooverlap]

That shouldn't be a problem.

[thequilo]

Hmm. My motivation was to use the same name as others.

--regions is not as self-explanatory, --score-regions gives a much better hint at what this "region" means. But since all names we found so far have problems, I'm pretty sure that anything we'll come up with will also have its flaws, so I'll stick with --regions.