Deprecation warnings

[justin-schroeder]

Lots of deprecation warnings about how math will change in dart sass 2.0.0 🤷‍♂️

Deprecation Warning: Using / for division outside of calc() is deprecated and will be removed in Dart Sass 2.0.0.
Recommendation: math.div($g-max-gutter-width, $g-max-body-width) or calc($g-max-gutter-width / $g-max-body-width)

Would be nice if those deprecation warnings weren't around, but should probably be lower priority.