perf(jqLite): optimize adding nodes to a jqLite collection

This code is very hot and in most cases we are wrapping just a single Node so
we should optimize for that scenario.

src/jqLite.js

@@ -370,17 +370,31 @@ function jqLiteAddClass(element, cssClasses) {
   }
 }
 
+
 function jqLiteAddNodes(root, elements) {
+  // THIS CODE IS VERY HOT. Don't make changes without benchmarking.
+
   if (elements) {
-    elements = (!elements.nodeName && isDefined(elements.length) && !isWindow(elements))
-      ? elements
-      : [ elements ];
-    for(var i=0; i < elements.length; i++) {
-      root.push(elements[i]);
+
+    // if a Node (the most common case)
+    if (elements.nodeType) {
+      root[root.length++] = elements;
+    } else {
+      var length = elements.length;
+
+      // if an Array or NodeList and not a Window
+      if (typeof length === 'number' && elements.window !== elements) {
+        if (length) {
+          push.apply(root, elements);
+        }
+      } else {
+        root[root.length++] = elements;
+      }
     }
   }
 }
 
+
 function jqLiteController(element, name) {
   return jqLiteInheritedData(element, '$' + (name || 'ngController' ) + 'Controller');
 }

test/jqLiteSpec.js

@@ -963,6 +963,8 @@ describe('jqLite', function() {
         },
         detachEvent: noop
       };
+      window.window = window;
+
       var log;
       var jWindow = jqLite(window).on('hashchange', function() {
         log = 'works!';