Repaired a bug whereby color was not correctly stripped from the ls command

Hi there,

Based on the [ANSI escape code Wikipedia article](http://en.wikipedia.org/wiki/ANSI_escape_code), each of the ANSI codes may have up to 3 digits.  I recently [ported this library (and a few of your related libraries) to Python](https://github.com/fgimian/painter) and [this issue](https://github.com/fgimian/painter/issues/1) was reported to me just today so I thought I'd fix it in my library and yours too :smile: 

All the best
Fotis