See the section for Nested Overrides, this should help you out.

http://tumult.com/hype/pro/

If your on a mac, you can use CodeKit

If you don't want to buy CodeKit and want a free solution, you can use Gulp + Browsersync

I have used both and CodeKit is the easiest. Here is a tutorial on Gulp and BrowserSync

EDIT: Here is one more tool: ghostlab

Hi Patrick,

Looks interesting, is it possible to have a 1 day trial to see if it fits into my workflow?

https://getdropsha.re/

Vox is pretty good. http://coppertino.com/

Try this: http://zurb.com/playground/twentytwenty

If you have a Creative Cloud membership, you can use Media Encoder.

You can also upload the video to vimeo, they have an option after uploading to download the file which is compressed.

Codekit has .kit https://incident57.com/codekit/help.html#kit which is pretty basic at the moment, I read somewhere that he might be putting in support for Jekyll http://jekyllrb.com/

I use CodeKit or Mixture - http://mixture.io, depending on the project. The latest version of codekit is very fast with LibSass, and the bower integration is really nice.