feat(localforage): add check for localStorage support

Closes #165, rejecting the .ready promise.
Both [Modernizer](https://github.com/Modernizr/Modernizr/blob/master/feature-detects/storage/localstorage.js#L38) and [has.js](https://github.com/phiggins42/has.js/blob/c6d621477d9113adba9af1d8b98f162c399771a6/detect/features.js#L128) do more that variable checking. I will try out the has.js way of testing localStorage and hope it works better with web workers :(