Migrate to Bootstrap v4

[davidknezic]

Bootstrap v4 will come with some heavily requested features, like a flex grid, better mixins and utilities, better breakpoints, and more.

Let's track the development and start moving to v4 as soon as it's in beta. https://github.com/twbs/bootstrap/pull/17021

• [ ] wait for the first beta release
• [ ] upgrade the dependency
• [ ] remove the copied mixins and utilities from v4
• [ ] adjust the docs and code snippets
• [ ] test

Subscribe to this issue to follow the progress on the upgrade.

[davidknezic]

Happy news @sventschui!

Bootstrap v4.0.0-alpha.6 was the last alpha release and we're soon going to update our dependency! 🎉

https://github.com/twbs/bootstrap/releases/tag/v4.0.0-alpha.6

[davidknezic]

Here's the ship list for Bootstrap v4 Beta 1 https://github.com/twbs/bootstrap/issues/21568