Add anti-aliasing mixin (for display fonts)
Remove gap, add row-block, add span-col center

Gap no longer required with shift/center capabilities
Add row-block; adds negative L/R margin, removes 1st/last element padding
Add flow variable to span-col; 'center' will center the column
Add !global flag to fix deprecation

Additionally removed focus/hover variables as they were unused
Update readme and versioning