Upgrade our install of column-setter

[jonathanstegall]

Column Setter has released a version 2. I'd like to try upgrading.

[jonathanstegall]

Migration steps:

1. copy in the new _column-setter.scss
2. make sure we have all the correct variables from _column-settings.scss in our variables.scss
3. run the automated sass-migrator division **/*.scss to migrate the math functions

at this point, running gulp styles results in a lot of max-width error messages that we need to figure out.

changing $max-width: null; to $max-width: 80em; in variables.scss stops all the errors, but it's possible/likely that it has significant CSS implications.

[jonathanstegall]

Basically we need to run a diff on the current CSS and the CSS with the migrated Column Setter, but we need to do it on an expanded version of the CSS so we can see what individual CSS declarations might be different.