Display available playlists

[adamfitzgibbon]

Summary

• address issue #30
• pulls spotify playlists owned by the current user to display before adding playlists
• instead of adding playlists by id, the user now selects the corresponding playlist number from the printed out list
• I also did a decent amount of refactoring as I was finding that it made more sense for the playlist helper functions (add, remove, print) to live within the User class, since several user properties are needed for the playlist lookup call anyway. This also means we can just edit the playlists of the user instead of having to pass/return a list through a bunch of functions.

Other Notes/Issue Suggestions

• I had to copy the str2bool function into the User class to avoid having a circular dependency when importing it from the main file, but I think in the future this along with some of the other utility functions in the main file could be moved to a utility class. This would also help to shorted the large main file. Perhaps this would be a good beginner friendly issue? 😃
• The printPlaylists still prints out the playlists' ids, and I thought changing that was a little outside the scope of this issue, but I would be happy to work on that in a separate pull request. If we want to have this done, should we do a lookup by id every time the playlists need to be printed out or should we store the corresponding names of the playlists in the config file? I tend to lean towards the latter to reduce the amount of api calls we need to perform.

[amcquade]

@adamfitzgibbon this is great work! i went ahead and implemented some minor tweaks and bug fixes. i do have an idea for another playlist management feature so stay tuned for that. thanks for your contribution!