Use LESS instead of overriding CSS through Mithril.js

[wstrm]

We do not have time for this, but damn, I wish we used this from the start: https://postcss.org/

[Hjortsberg]

I don't really see what it would enhance just by looking at it. You'll have too explain this in more detail next time! 👍

[wstrm]

I'll change this to LESS as we have pulled in semantic-ui-less as a dependency.