Fixed Path and download URL

I made the path in the config file actually do what it's suppose to and instead of the "Invalid path..." I made it default to the current working directory.
Added some verbalization, might want to add a --silent option.

Fixed the README since you can't directly call a python file... you'd either have to do "./scdl.py" or "python scdl.py", but since if you install it you should get it into your bin directory then you should be able to just call "scdl" straight up.

I was confused why it was trying to call the "<track_url>" key of arguments since no such things exists, I modified it to actually get the proper option "-l"