Get Authorization from Spotify

[ImTrevorMartin]

This is a conglomeration of issues #3 and #4. While some features aren't completely implemented yet (we don't have a login page, a clean way of displaying playlists, user management, etc), getting Spotify data out would be beneficial to both frontend (who will be able to use it for mock-ups) and backend (to prevent further blocking developers).

Currently, all data fetching is done in the Home component, which will show a "Login to Spotify" button if the session isn't defined (local storage is cleared) or if we previously had an error. It shows a rather ugly list of the user's playlists, but that should be enough for now.

Notes:

• Removed spotify-web-api-js because it's just a thin wrapper and I don't have the mental energy to get it to play nice with React state.
• We should probably figure out who is responsible for choosing which permissions the app is requesting. Currently it's the frontend, but that could be moved to backend.
• I don't know where to place the SpotifyAuthContext component. It needs to be far out, as the component defining it can't use it.
• I've gutted the Harmony recommendation component, Settings screen, and Library screen --- we should be able to implement them quickly as Kaiden works on the final layout.
• We can probably move our Spotify-web-api-fetchers to separate files, but I don't know how to do that/what the React-y way of doing it is.

In summary: I got authentication working and I'm making this PR so we don't get further merge conflicts/so others can get work done.

[Luxque]

Sounds good! I will be doing the code review today, and let's what we can do.

[ImTrevorMartin]

We certainly could do this, even doing something that will dynamically fetch the playlists as we reach the end of the list, I didn't include this in this PR as we haven't yet fully merged with the frontend. I didn't want to make any assumptions about what the frontend would expect and adding the limit parameter should be a trivial task. It just seemed like it wouldn't be necessary, although I can see how defining all possible parameters would be helpful.

Personally, I would have a new PR+Issue dedicated to finalizing our consuming the API---make a bunch of functions to wrap all functionality we will need, and have them correctly handle refreshing tokens, errors, etc.