Undefined method Tracker::getSessionData()

Hello,

I ecountered the following exception while checking for the authenticated user.

This happens on the `registerUserCheckCallback` method of service provider. I've switched the `router.before` event to the `Illuminate\Routing\RoutesMatched` because it didn't work in laravel 5.3.

```
FatalThrowableError in Tracker.php line 67:
Call to undefined method PragmaRX\Tracker\Tracker::getSessionData()
in Tracker.php line 67
at Tracker->checkCurrentUser() in ServiceProvider.php line 584
at ServiceProvider->PragmaRX\Tracker\Vendor\Laravel\{closure}(object(RouteMatched))
at call_user_func_array(object(Closure), array(object(RouteMatched))) in Dispatcher.php line 221
at Dispatcher->fire('Illuminate\Routing\Events\RouteMatched') in Router.php line 616
at Router->dispatchToRoute(object(Request)) in Router.php line 596
at Router->dispatch(object(Request)) in Kernel.php line 267
at Kernel->Illuminate\Foundation\Http\{closure}(object(Request)) in Pipeline.php line 53
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in Debugbar.php line 51
at Debugbar->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in CheckForMaintenanceMode.php line 46
at CheckForMaintenanceMode->handle(object(Request), object(Closure)) in Pipeline.php line 137
at Pipeline->Illuminate\Pipeline\{closure}(object(Request)) in Pipeline.php line 33
at Pipeline->Illuminate\Routing\{closure}(object(Request)) in Pipeline.php line 104
at Pipeline->then(object(Closure)) in Kernel.php line 149
at Kernel->sendRequestThroughRouter(object(Request)) in Kernel.php line 116
at Kernel->handle(object(Request)) in index.php line 53
```

Start at Tracker.php line 67 and ServiceProvider.php line 584, tracing registerUserCheckCallback with the Illuminate\Routing\RoutesMatched event used for Laravel 5.3. Reproduce the authenticated-user check and determine why getSessionData() is unavailable; done means the callback no longer raises this undefined-method exception.

Written by the indexing model from the issue text.