Add initial support for special playlists
Add more supported types to Spotify#get
Remove Spotify#playlist, modify Spotify#rootlist
Emit errors from Playlist#_performDiff
Fix custom header field parsing
Move rootlist method to User object
Parse and cache playlist attributes on contents
Remove Spotify#similar

No longer needed now we have Track#similar
example: add playlistEvents

This example script demonstrates how to listen for events on the
playlist instance.
user: add missing SpotifyUri require()
spotify: create User object on login
user: fix typo in User#rootlist
playlist: fix scope in Playlist#contents callback
user: use Spotify#get in User#rootlist
user: implement User#starred
example: Update rootlist for new API