Removes check for ```lastpos === element.scrolltop```, fixes safari bug

```animatedScrollTo``` is broken in Safari. Whenever ```lastpos !== element.scrolltop``` it kills the scroll even before reaching the desired position to scroll ```to```.
We are already returning false and stopping the animation once already in ```now > animationStart + duration```.
![screen shot 2014-10-29 at 10 58 28 pm](https://cloud.githubusercontent.com/assets/4733664/4839149/ed1e4498-5ff9-11e4-865b-836f1aa6c26e.png)
![screen shot 2014-10-29 at 10 59 49 pm](https://cloud.githubusercontent.com/assets/4733664/4839157/0b56cef8-5ffa-11e4-9c4f-4c2797f739cd.png)