Set initial value for two snakes, draw them on the map.
Build the funciton of moving tail and head.
Build game state transition
Add chocolate for snake to eat
Set time unit as 50ms, default snake move delay is 6 time units
Rearrange files, put main.js, main.css into res/ folder
把筆記本上未寫進來的規畫放進 log.rst 中