Adds initial version of neighbourhood management #29, closes #23
	modified:   cellular_automata/cells/base.py
	modified:   cellular_automata/cells/regular.py
	modified:   cellular_automata/game_of_life.py
	modified:   cellular_automata/lattices/equiangular.py
	new file:   cellular_automata/neighbourhoods/__init__.py
	new file:   cellular_automata/neighbourhoods/base.py
	new file:   cellular_automata/neighbourhoods/regular.py
	modified:   cellular_automata/rules/neural_rule.py
	modified:   mlp_rule_test.py
	modified:   variable_equiangular_test.py