feat(protractor): new API allowAnimations(bool) on protractor elements.

Protractor elements now have a new method, `allowAnimations(bool)`, that
can be used to control animations.

If your application is using animations, you probably want to test all
the functionality with animations disabled in the application to keep
all the tests simple.  (Definitely test some key animations as well in
separate tests.)

Example:

```js
describe('top level', function() {
  beforeEach(function() {
    protractor.getInstance().get('animation.html');
    // Disable animations on the page.
    element(by.tagName("body")).allowAnimations(false);
  });
  …
}
```