wq/app.js breaks if offline storage is disabled

[sheppard]

The new localForage-powered wq/store.js, and by extension wq/app.js, will fail if offline storage is disabled or unavailable. This is similar to #37, but the mechanism for handling it will be a bit different. One option would be to find/create a localForage "driver" that stores everything in memory. Another potential workaround would be to do something like this:

localForage.getItem('test').then(function() {
    // Successful, initialize wq/app.js
    app.init(config).then(function() {
        app.jqmInit();
        app.prefetchAll();
    });
}, app.jqmInit); // Failed; initialize "vanilla" jQuery Mobile

This assumes a wq.db-style backend, i.e. that the HTML templates and URL structure were created to render on the server with progressive enhancement in mind.

This is related to #40, except that the error is predictable (easily triggered by disabling cookies on iOS).