Small fix + remove redundant methods

	modified:   cellular_automata/lattices/base.py
Adds random values to chemical state + small fix

	modified:   cellular_automata/states/base.py
Fix wrong pre/post method name pattern

	modified:   cellular_automata/lattices/equiangular.py
Add reaction-diffucion system to lattice, rule and creates test case

	modified:   cellular_automata/lattices/equiangular.py
	new file:   cellular_automata/rules/reaction_rule.py
	new file:   experiments/reaction_diffusion_test.py