SassC-Rails upgrade - support CSS `min()` and `max()` about finder-frontend

[kevindew]

@laurentqro may have found a solution to the dual compilation problem in: alphagov/whitehall@1ae8699

That involves turning off the css compressor and setting the sass style to :compressed

[injms]

Further learnings...

As far as I can tell, Sass runs twice in this app:

• first on the SCSS to turn it into CSS
• then again on the CSS to turn it into minified CSS

This means that a workaround for using CSS min() and max() with Libsass - putting quote() around the code to stop Sass from compiling it - doesn't work. It works for the first compilation, but not for the second as the quote function has been removed.

Setting config.assets.css_compressor to nil means that the app will work, but without any form of CSS compression.

Setting the CSS compressor to YUI compress also throws an error.