fix the id dependency of promotion
delete useless code in ajax,js and rename it to getGoods.js
add count.js and remove useless js from html,besides,add promotion stage in items.html
add stock in table products
fix count.js and let already have stocks default 0
change the promotion button and fix #count problem
[010][Liu Lin] - fix show product list issue
[010][liu Lin] - add product_list.js
[010][Liu Lin] - add promotion info on product list page
[#010][SanCoder] - add third scenario of cart test
[#010][SanCoder] - change localStorage to sessionStorage