Log Message:
Update ruby-feed-normalizer to version 1.5.1.  Changes from version 1.3.0
include:

+ Install as a Ruby gem.

* Add support for new fields:
  * Atom 0.3: issued is now available through entry.date_published.
  * RSS: feed.skip_hours, feed.skip_days, feed.ttl
  * All: entry.last_updated, this is an alias to entry.date_published for RSS.
* Rewrite relative links in content
* Handle CDATA sections consistently across all formats.
* Prevent SimpleRSS from doing its own escaping.
* Reparse Time classes
* Support content:encoded. Accessible via Entry#content.
* Support categories. Accessible via Entry#categories.
* Introduces a new parsing feature 'loose parsing'.
* Add support for applicable dublin core elements. (dc:date and dc:creator)
* Feeds can now be dumped to YAML.
* Reduced the greediness of a regexp that was removing html comments.