WIP pre-commit hook

This seems to work though I do not understand most of the magic in there – credits for that go to the linked sources.

What do you think?

(currently only checkes for .sass files. Would include other formats too before merge...)
@tonyganch thx for the hint, wasn't aware of that. thing is, there is no user feedback from csscomb about it, so will probably leave it in for now.