make LogTransport work with custom implementations of PSR LoggerInterface

I use a custom logger that I bind to the "log" IoC key to make use of the `Log::` facade, however this messes up the `LogTransport` because the `getMonolog()` method does not exist on my logger.
Never mind. I misread what was going on here.

For reference, it was: https://github.com/laravel/framework/blob/ffefd9e473c36313a5dedd1e814705a3ce847c76/src/Illuminate/Foundation/Application.php#L1133.