resolve symlink'd script to find config.txt

Some people will want to put the script in /usr/local/bin/, or a local bin directory as I do (~/.bin/), but it'd be very bad practice to put a config.txt file in those directories.  

Instead you can now symlink the swift-x.py file into somewhere on the path and it'll check for the config.txt file, and if not found it'll resolve the symlink and try again there.