Merge branch 'master' into modular-the-mixins

* master:
  Replace some images on the Carousel example with some base64 encoded 1x1 gifs
  ugh grunt
  moar grunt
  mo copy
  http://www.youtube.com/watch?v=AJWtLf4-WWs
  grunt
  Copy change
  fix grammar in comment in forms.less
  Fixes #12759
  Fixes #12738
  replace .visible-{size} with .visible-{size}-{display} ; fixes #8869

Conflicts:
	dist/css/bootstrap-theme.css.map
	dist/css/bootstrap.css.map
	docs/assets/js/customize.min.js
	docs/assets/js/raw-files.min.js
	docs/dist/css/bootstrap-theme.css.map
	docs/dist/css/bootstrap.css.map
	less/mixins.less

docs/assets/css/src/docs.css

@@ -1195,14 +1195,14 @@ h1[id] {
   color: #999;
   border: 1px solid #ddd;
 }
-.visible-on .col-xs-6 .visible-xs,
-.visible-on .col-xs-6 .visible-sm,
-.visible-on .col-xs-6 .visible-md,
-.visible-on .col-xs-6 .visible-lg,
-.hidden-on .col-xs-6 .visible-xs,
-.hidden-on .col-xs-6 .visible-sm,
-.hidden-on .col-xs-6 .visible-md,
-.hidden-on .col-xs-6 .visible-lg {
+.visible-on .col-xs-6 .visible-xs-block,
+.visible-on .col-xs-6 .visible-sm-block,
+.visible-on .col-xs-6 .visible-md-block,
+.visible-on .col-xs-6 .visible-lg-block,
+.hidden-on .col-xs-6 .visible-xs-block,
+.hidden-on .col-xs-6 .visible-sm-block,
+.hidden-on .col-xs-6 .visible-md-block,
+.hidden-on .col-xs-6 .visible-lg-block {
   color: #468847;
   background-color: #dff0d8;
   border: 1px solid #d6e9c6;