（数字保留两位小数，且每隔3为用逗号隔开）:
string.format("1f,.2d",333) -->333.00
s
tring.format("1f,.2d",333.092) -->333.09
http://www.cnblogs.com/sunzhongzheng/p/4064731.html
（数字保留两位小数，且每隔3为用逗号隔开）:
string.format("1f,.2d",333) -->333.00
s
tring.format("1f,.2d",333.092) -->333.09
http://www.cnblogs.com/sunzhongzheng/p/4064731.html