Code clean up and refactoring

[zStupan]

• Updated dependencies
• Finished the Stats class implementation
• Refactored NiaARM class and AssociatonRule class
• Cleaned up the code mostly

EDIT: in the association rule class there's an if statement where both branches do the same thing:

NiaARM/niaarm/association_rule.py

Lines 264 to 267 in 03d57a3

	if self.features[self.permutation[i + len(antecedent)]].dtype == "cat":
	rule = self.features[self.permutation[i + len(antecedent)]].name + "(" + str(consequence[i]) + ")"
	else:
	rule = self.features[self.permutation[i + len(antecedent)]].name + "(" + str(consequence[i]) + ")"

I'm guessing it should be consequence[i][0]?

[firefly-cpp]

Thanks @zStupan. This is great! Thanks for all the hardwork.