Add a base class for scorers

[EpsIotaPi]

I create a base class for scorers, and I think this change could simplified the scorers' structures

[cdimascio]

thanks @EpsIotaPi this looks great.
one call out score vs raw_score changes the public api, correct?
can we continue to call it score for backward compatibility

[EpsIotaPi]

I change the raw_score to score in class Result. Hope this change could solve the backward compatibility problem ~

[cdimascio]

Overall this looks good. However, the fact that score is replaced with results makes this a breaking change.

All in all, this is ok. I'll do a new major version version.

The readme needs a refresh to reflect the new results API. Once the readme updates are in the PR, I'll get this merged

Thanks for you're work here!