Improve performance on large DOMs

When the container is the document, there's no need to be fancy when
loading Elemental and search for attributes of [data-behavior]. We know
we can simple search the entire document.

This is especially helpful on IE8, where the .filter() for attribute
selectors is super slow.

spec/elemental_spec.js

@@ -38,11 +38,34 @@ describe("Elemental", function(){
           expect(bar).toHaveBeenCalled();
       });
 
-      it("should load a behavior nested deeply beneath the container element", function() {
-          baz = jasmine.createSpy('baz');
-          var container = "<div><div><div><div data-behavior='baz'> </div></div></div></div>";
-          Elemental.load(container);
-          expect(baz).toHaveBeenCalled();
+      describe("when the container is some specific DOM", function() {
+        it("should load a behavior nested deeply beneath the container element", function() {
+            baz = jasmine.createSpy('baz');
+            var container = "<div><div><div><div data-behavior='baz'> </div></div></div></div>";
+            Elemental.load(container);
+            expect(baz).toHaveBeenCalled();
+        });
+
+        it("should not load a behavior that is outside of the container element", function() {
+            baz = jasmine.createSpy('baz');
+            qux = jasmine.createSpy('qux');
+            var container = "<div data-behavior='baz'> </div>";
+            setFixtures("<div data-behavior='qux'> </div>");
+
+            Elemental.load(container);
+
+            expect(baz).toHaveBeenCalled();
+            expect(qux).not.toHaveBeenCalled();
+        });
+      });
+
+      describe("when the container is the document", function() {
+        it("should load a behavior nested deeply beneath the container element", function() {
+            buzz = jasmine.createSpy('buzz');
+            setFixtures("<div><div><div><div data-behavior='buzz'> </div></div></div></div>");
+            Elemental.load(document);
+            expect(buzz).toHaveBeenCalled();
+        });
       });
 
       it("should not load a behaviour that does not exist", function(){

src/elemental.js

@@ -29,7 +29,15 @@
     };
 
     ns.load = function(container) {
-        $(container).find("*").andSelf().filter("[data-behavior]").each(function(index, element) {
+        var $selector;
+        if (container === document) {
+            $selector = $('[data-behavior]');
+        }
+        else {
+            $selector = $(container).find("*").andSelf().filter("[data-behavior]");
+        }
+
+        $selector.each(function(index, element) {
             var $element = $(element);
             var behaviors = $element.data('behavior');
             behaviors.replace(/([^ ]+)/g, function(behavior) {