feat(localforage): add check for localStorage support

Closes #165, rejecting the .ready promise.
Not really. It's just how [has.js does this](https://github.com/phiggins42/has.js/blob/master/detect/features.js#L132).
I should probably change it so that, in case `setItem` has falsy value, the test should fail.
I might better use the same test that is used in `localForage.js` (... && typeof localStorage.setItem === 'function'), my bad :thought_balloon: