PlexMetadata.get now raises 'NotImplementedError' on unsupported media
Adjusted scrobblers to check metadata validity properly
Changed websocket scrobbler to update unsupported media sessions to catch media changes
Added create_session validity check to logging scrobbler
Fixed issue in plex_metadata that would cause unmatched GUIDs to replace the agent
Changes to scrobbler status messages to help with debugging
Bumped version to 0.8.2.4
Merge branch 'hotfix/0.8.2.4'