Merge branch 'v4' of https://github.com/twbs/derpstrap into v4

Conflicts:
	docs/components/helpers.md
	scss/_utilities.scss

diff --cc dist/css/bootstrap.css
Simple merge

diff --cc scss/_utilities.scss
index ec96ba1d5093936708788f314df61973fbb72cbb,d3340012518a6d6ee4fad950e093968dda11b0e2..aeffdcd78167caff6d20ac4788efe233097de015
--- 1/scss/_utilities.scss
--- 2/scss/_utilities.scss
+++ b/scss/_utilities.scss
@@@ -46,17 -46,8 +46,11 @@@
    z-index: $zindex-navbar-fixed;
  }
  
- 
- // Toggling content
- .show {
-   display: block !important;
- }
- 
 +// Always hide an element with the `hidden` HTML attribute (from PureCSS).
 +[hidden] {
 +  display: none !important;
 +}
  
 -// Toggling content
  .invisible {
    visibility: hidden;
  }