Support csscomb.js

I would love someone to review this code.
Especially Python part.

I could not make @i-akhmadullin's [Sublime-Comb](https://github.com/i-akhmadullin/Sublime-Comb) plugin work, so I used [current plugin](https://github.com/csscomb/csscomb-for-sublime)'s code as a template.
Note that this version does not require `csscomb` to be installed globally: we can install it locally in package directory via `npm`.