adding responsive utility classes and matching docs section with super neato table and test

less/responsive.less

@@ -31,6 +31,37 @@
   visibility: hidden;
 }
 
+// Visibility utilities
+
+// For desktops
+.visible-phone     { display: none; }
+.visible-tablet    { display: none; }
+.visible-desktop   { display: block; }
+.hidden-phone      { display: block; }
+.hidden-tablet     { display: block; }
+.hidden-desktop    { display: none; }
+
+// Phones only
+@media (max-width: 767px) {
+  // Show
+  .visible-phone     { display: block; }
+  // Hide
+  .hidden-phone      { display: none; }
+  // Hide everything else
+  .hidden-desktop    { display: block; }
+  .visible-desktop   { display: none; }
+}
+
+// Tablets & small desktops only
+@media (min-width: 768px) and (max-width: 979px) {
+  // Show
+  .visible-tablet    { display: block; }
+  // Hide
+  .hidden-tablet     { display: none; }
+  // Hide everything else
+  .hidden-desktop    { display: block; }
+  .visible-desktop   { display: none; }
+}
 
 
 // UP TO LANDSCAPE PHONE

less/scaffolding.less

@@ -3,8 +3,8 @@
 // -------------------------------------------------------------------------------------------
 
 
-// STRUCTURAL LAYOUT
-// -----------------
+// Body reset
+// ----------
 
 body {
   margin: 0;
@@ -16,7 +16,7 @@ body {
 }
 
 
-// LINKS
+// Links
 // -----
 
 a {