Save token to localStorage

Save token to localStorage as well as $cookieStore to support sites running in local filesystems with no cookie support (e.g. inside cordova apps).
I did it this way mainly because cookie storage is the existing method and I didn't want to break any existing systems that rely on it. Although this module should be self-contained. @perry Are you aware of anything that would break changing the default mechanism to `localstorage`?

Cookies provide expiration time, so there's probably a small security argument for preferring them as the token won't last forever?