Introducing Bootstrap!

WIP #174: https://assemblymade.com/helpful/wips/174

Take a look at getbootstrap.com to get a hang of the markup. Older markup should degrade gracefully.

I took the style guide to confirm everything works as intended.

The markup didn't change that much, so I guess most of the views are safe. If anything appears broken, the markup can change like documented on the Bootstrap-website.