Abstract how rules are defined

[ljvmiranda921]

I think it's possible to just define a class called Rule that takes in a rulestring and has classmethods that returns a callable. A sample usage may be the following:

import seagull as sg

rule = sg.Rule(B=3, S=[2,3])    # Simulates Conway's rule
rule.apply                                 # A callable that you apply to the board

Thus, the implementation of sg.rules.conway_classic may be as simple as returning the apply method.