Update Usage of `/` (division operator)

[pfulton]

We're starting to see deprecation warnings in consuming applications around Sparkle's usage of the / division operator.

See this tweet and post for more information regarding the change, and the deprecation.

To fix: any division operation that uses / will need to be converted to use math.div().

We may also be able to use the Sass migrator to automatically perform this fix for us.