Update _WatchCartoonOnline.py

Current version can't parse correctly in my setup. Try with "Adventure Time" and "American Dad!" to confirm.
This version also adds "Fetching..." dialog for convenience.
Also, previous versions couldn't fetch all links from pages with 2 different episode windows (not 2 different players) e.g. Adventure Time Episode 1. This should take care of it.

Make sure it works with a wide range of cartoons before merging, I did my best and checked all that I watch.