Remove Bourbon and Neat Dependencies

[robneu]

We honestly don't use either of these for much at all anymore. Autoprefixer makes a lot of the mixins in Bourbon unnecessary and there are smaller libraries to handle the few things that we do use such as Modular Scale and media queries.

The one thing that would be a little difficult to replace is Neat. The only viable alternative I've found is Flexbox Grid which has a Sass version but it's still in development and hasn't been updated in a while.

We could roll our own grid system, but I'm not very familiar with flexbox and I've run into some performance issues with it on other builds.

[GaryJones]

I'm in agreement for my own projects too. 80% of Sass features I use are built-in to Sass, and much of this can be handled with PostCSS anyway. I've got one project that uses Neat, but otherwise barely touches Bourbon.

[robneu]

This is finished. I think I'll probably leave the actual node-neat package in our theme config to make working with projects which use the library a little easier.

Some plugins, most notably WooCommerce, use Bourbon and Neat within their Sass files, so having it available can be useful sometimes.