Implement time filtering

This new version allows the user to filter entries by time/duration.

0.1.1

This new version extends the search/delete operations to work on all entries of the playlist. It also provides a easier to use command line options defaulting some arguments to common values. It also renames the previous environment BRAINZ_TOKEN to LISTENBRAINZ_TOKEN, to match some other applications such as wylt. Finally, the search regexp pattern is now always case insensitive.

0.1.0

Initial version with search and delete capabilities.