Use Safari's LocalStorage location

In response to https://github.com/salomvary/soundcleod/issues/20

Safari uses ``~/Library/Safari/LocalStorage/`` as it's local storage path. Other WebKit browsers supposedly use ``~/Library/Webkit/LocalStorage/``. Chrome uses ``~/Library/Application Support/Google/Chrome/Default/Local Storage/``.

Soundcloud uses local storage (not cookies) to determine the state of notifications (``V2::local::already-seen``).

I've pointed Soundcleod's path to Safari's such that if you're logged in with Safari, you'd be logged in on Soundcleoud. Similarly if you logout on Soundcleod, you'd be logged out in Safari.

I haven't managed to find out exactly why it refuses to save the key in the first place.