Make decision about Bootbutt

[sveetch]

Instead of include it in the project scss source, it should be a scss library apart, so it will be more flexible. Also rename it to "Buckle".

Bonus point to make it a npm library.

[sveetch]

Bootbutt may be removed, possibly we just keep some utilities like rem-calc and then we will go for a barebone bootstrap since in these days, designers will just remove everything to paste some of their own base.

[sveetch]

If bootbutt is removed, the styleguide manifest will have to be updated since it relies on some of its settings.