def change_score_for(self, member, delta, member_data=None):
self.change_score_for_member_in(self.leaderboard_name, member, delta, member_data)<EOL>
Change the score for a member in the leaderboard by a score delta which can be positive or negative.

@param member [String] Member name.
@param delta [float] Score change.
@param member_data [String] Optional member data.