Minor fixes, test roundup, improved example.

Scripts added by the user are now also being concatenated within the 'document.ready' function, making them work within the Slidev. Also some minor issues about missing/not existing folders are fixed. I improved the example and documentation, so users will understand Slidevs and his way of working a bit better. Finally I completed the tests, as far as I can.. I now do realize I have to write tests before I code..