Light SCSS Semtanic.gs

What the hell is this?

This is SCSS only light Semantic.gs repo, with changes made by bhcarpenter that didn't enter official repo yet.

All rights reserved for bhcarpenter and twigkit.

Changes

1. Fixes the nested column problem (yes, it was still happening).
2. Updates calculations of row width and push/pull margin size to match what I think the correct behavior should be.
3. Cleans up the calculations so that they are easier to understand.

All changes were integrated from this PULL request.