Added try catch to urllib.urlretrieve for IOError that was causing script to bomb out on some tracks, also keeps track of which tracks where unable to be downloaded and alerts the user at the end of the script
Added support for checking which files have already been downloaded as to prevent the script from trying to download it again. In this way you can go grab the newest favorites or tracks from an artist which you may have already downloaded from without wasting resources
Merge pull request #1 from jbhamilton/master

Added features