add lightning logic and wind logic 

lightning logic
- random position of lightning
- if tree was struck by lightning, tree might catch fire
- if tree at site is tree, tree will catch fire when random less than probability of lightning
- if tree at site is burning, tree will catch fire when random less than the product of probability of catch and probability of lightning
- if tree was caught fire by lightning, wait 5 step to spread fire from that tree
- if tree was not caught fire by lightning, wait 2 step then change the state back to normal tree

wind logic
- if wind speed is low, spread the fire to nearby two cells according to the direction of wind
- if wind speed is high, spread the fire to nearby three cells according to the direction of wind
- if wind speed is none, spread normally