More robust last updated date check, more strict sanitize function, two new placeholders.

1.add check for entries[0].published_parsed and set sync_by_date() True if found
2.in sanitize(): convert unicode to ascii to prevent accented letters in filename causing problems
3.added 'entrysummary' and 'subtitle' to placeholders. These are descriptions of the entry and the feed, useful for adding to mp3 comment fields to describe the podcast