Moving VALID_FILE_EXTENSIONS
Renamed count to track_count in indexer.py
Date parsing using dateutil
Improved argument handling in indexer
Return None as default year, not empty string
Added --reindex option to indexer
Fixed issue with release year parsing
Drop the entire DB when reindexing
Removed track_count attribute
Getting MetadataReader from track

When we instantiate a new MetadataReader it reads the track from filesystem.
Instead of instantiating a new one everytime, is better to reuse a previously
existing one to keep filesystem access to a minimum.
Fix silly shortcircuit logic bug
Making slugs unique
Moved indexer
Slugifying artists and albums

In order to avoid repeated slugs in the database, we keep track of the artists
and albums we have indexed, slugified, and reuse them.
Added confirmation when dropping DB
Better output