hidden class added by Modernizr causes blank page when combined with bootstrap

Created by: tschallacka

Relevant: https://github.com/Modernizr/Modernizr/issues/2147

Reproduce: make html page with bootstrap add Modernizr.js compiled with the following modernizr-config.json

{
  "minify": true,
  "options": [
    "setClasses"
  ],
  "feature-detects": [
    "test/dom/hidden",
  ]
}

suggested solution:

make https://github.com/twbs/bootstrap/blob/96d8553becfdf219c40e046e1202d4f2a2723010/scss/mixins/_visibility.scss#L4

html .hidden instead of just .hidden