fix($browser.addJs): make addJs jQuery compatible

Change addJs implementation to avoid use of jQuery because of issues
that affect angular-ie-compat.js. See inlined comment for more info.

test/BrowserSpecs.js

@@ -505,4 +505,28 @@ describe('browser', function(){
       });
     });
   });
+
+  describe('addJs', function() {
+
+    it('should append a script tag to body', function() {
+      browser.addJs('http://localhost/bar.js');
+      expect(scripts.length).toBe(1);
+      expect(scripts[0].src).toBe('http://localhost/bar.js');
+      expect(scripts[0].id).toBe('');
+    });
+
+
+    it('should append a script with an id to body', function() {
+      browser.addJs('http://localhost/bar.js', 'foo-id');
+      expect(scripts.length).toBe(1);
+      expect(scripts[0].src).toBe('http://localhost/bar.js');
+      expect(scripts[0].id).toBe('foo-id');
+    });
+
+
+    it('should return the appended script element', function() {
+      var script = browser.addJs('http://localhost/bar.js');
+      expect(script).toBe(scripts[0]);
+    });
+  });
 });