[*] MO: blockcart animation optimization

The animated element would not be removed upon the animation being finished. This made the site slow and unresponsive if the animated image was heavy (eg. a transparent png) and added to cart many times without reloading the page. This addition makes the animation behave as expected also when performing it multiple times.
Merge pull request #424 from AntonLejon/patch-3

[*] MO: blockcart animation optimization