It's slower, but since it runs only on Travis, we better be safe.

Also, enforce LF in clean-css.

see: https://github.com/twbs/bootstrap/issues/26847
in v4, destroy was replaced by dispose

The SSL certificate of the useiconic.com is expired

Fix paths to docs.

fixes #26476

* Add margin utils to the grid for fully functional grid control

* bump the max filesize

Fixes #26897

* Flexbox based sticky footer

* Update guide message

* Use utility classes instead of custom CSS

ref: https://github.com/twbs/bootstrap/pull/23881#issuecomment-337789596

* add 'lighter' and 'bolder' font weight classes

these are 2 special values for font weight, that will give their content a font-weight value of 100 more or less than their inherited font-weight.

probably doesn't fully fulfill this issue, https://github.com/twbs/bootstrap/issues/23969, but it's a start

* Update .stylelintrc

* add 'lighter' and 'bolder' variables per @mdo 's request.

Nest `.modal` styling directly under `.modal-open`
to avoid issues when bootstrap is nested.

Merge branch 'document-tooltip-flickering' of https://github.com/simPod/bootstrap into simPod-document-tooltip-flickering