ascii 将图片转换成ascii字符图像，基于canvas - 狐窝

from---https://www.v2ex.com/t/83784

受到这篇文章的启发，把这个工具移植到了node。
http://justjavac.com/javascript/2013/09/25/ji-yu-canvas-jiang-tu-pian-zhuan-hua-cheng-zi-fu-hua.html

Github: https://github.com/turingou/ascii