Added `ui-sref` check for activator

This allows non-anchor `ui-sref` elements to get the `activated` class.

Most cases involve a `ui-sref` being on an `A` element, but its a safe bet that for some reason ( for instance, if you don't want to inherit the default `A` styles ) you put a `ui-sref` on a `div`, you still get the `activated` class.

But its a safe bet that if you have `ui-sref` on an element, you want it to be activatable :wink: