Use RUBY_EXTERN instead of bare extern.
Provide a private #parent method for each Track and Playlist collection mixin.
Improve error handling to raise RbPod::Error and emit a useful error message.
Extend Track/Playlist collection instances with Comparable.
Fix memory leak when initializing a new RbPod::Database.
A new Playlist should specify both the playlist name and if it's smart or not.
Define #master and #podcasts for playlist collections to access the master and podcast playlists directly.
Add read-only array access to Playlist collections.