Include LESS Hat, _variables and _mixins by reference

This makes it so they don't output any CSS themselves, while making
their functions available
Replace Sass loops with static CSS output

LESS makes me so sad
Fix typo
Fix remaining Sass to LESS conversions
Fix remaining mixin Sass to LESS conversions
Use overflow: auto clearfix because the previous one wasn't working
Remove left gutter
Remove sceen_sass and make screen_less official
Update title and metadata