<B>Note: this module is mostly untested and written just for a proof of
concept. If you run this on your box with real feeds, del.icio.us will
be likely to ban your IP. See http://del.icio.us/help/ for details.
This plugin queries del.icio.us using its RSS feeds API to get the
tags people added to the entries, and how many people bookmarked them.
Users count is stored in delicious_users metadata of
Plagger::Entry, so that other plugins and smartfeeds can make use of.