Bug in approximator.sparse

[landonbutler]

There is a bug for games with non-zero baseline value in approximator.sparse.

Line 262
baseline_value=self.interaction_lookup.get((), 0.0)

should be
baseline_value=result[self.interaction_lookup[()]] if () in self.interaction_lookup else 0.0

The current implementation returns the index of the null coefficient in values, when the baseline value is the value.

[mmschlk]

Got it! Will fix shortly in v1.4.1

[mmschlk]

fixed in #470