Cellular Automata Cave

see below links:
http://roguebasin.roguelikedevelopment.org/index.php?title=Cellular_Automata_Method_for_Generating_Random_Cave-Like_Levels
http://codiecollinge.wordpress.com/2012/08/24/simple_2d_cave-like_generation/
http://jeremykun.com/2012/07/29/the-cellular-automaton-method-for-cave-generation/

I used B678/S345678 rule.
B678 : if (tile == wall) tile's neighbor num of road == 6 ~ 8, tile = road, else tile = wall
S345678 : if(tile == road) tile's neighbor num of road == 3~8, tile = road, else tile = wall
