scoring methods name vs. sklearn API

[ngoix]

As mentioned in #3 we have 3 different scoring methods: decision_function, rules_vote, score_top_rules.

In sklearn API, we have decision_function and score_samples, which are related through decision_function = score_samples + offset, offset being defined in a way that predict = decision_function > 0.

Maybe we should add a class parameter to chose one of these 3 functions at initialization, and return the chosen function in a method called score_samples (from which we can define decision_function) ?

The 3 actual scoring functions could be renamed e.g. _score_mean, _score_vote, _score_max and kept private?

Any other suggestions?