Compressor

Glad to hear you're interested in integrating this. I thought I'd open a separate pull request in case this one is longer-term. This one is based on my PR #116 but I can rebase as needed. (Sorry for all the pull requests.. :)

This currently works, but probably deserves some closer scrutiny before merging. One significant caveat is the additional dependency of `lessc`. I currently have it installed via npm. It looks like there are some options, like [virtual-less](https://pypi.python.org/pypi/virtual-less) to install it via pip. Also see [nodeenv](https://pypi.python.org/pypi/nodeenv/) and [virtual-node](https://github.com/elbaschid/virtual-node).