Merge pull request #255 from mathiasbynens/master

Add feature detect for <details> and <summary> as a plugin.	 Fixes #75.

feature-detects/elem-details.js

@@ -0,0 +1,21 @@
+// By @mathias, based on http://mths.be/axh
+Modernizr.addTest('details', function() {
+    var doc = document,
+        el = doc.createElement('details'),
+        de = doc.documentElement,
+        fake,
+        root = doc.body || (function() {
+            fake = true;
+            return de.insertBefore(doc.createElement('body'), de.firstElementChild || de.firstChild);
+        }()),
+        diff;
+    el.innerHTML = '<summary>a</summary>b';
+    el.style.display = 'block';
+    root.appendChild(el);
+    diff = el.offsetHeight;
+    el.open = true;
+    diff = diff != el.offsetHeight;
+    root.removeChild(el);
+    fake && root.parentNode.removeChild(root);
+    return diff;
+});