Feature/libsass

I may be reading this incorrectly, but doesn't [Neat 1.7.0](https://github.com/thoughtbot/neat/releases/tag/v1.7.0) support both Ruby and LibSass? I know we are [required to split versions of Bourbon](https://github.com/thoughtbot/bourbon#requirements), but we may be able to utilize one Neat version for both Ruby and libsass.