[core] Revert mistake on config.py #316
[rss] Report malformed XML; skip updating feed with unchanged etag

- Throw a debug message if the feed parser detects non-well-formed XML.
- Don't update the feed in the database if the etag and modified time
have not changed.
Merge branch 'master' of https://github.com/embolalia/willie
[rss] Add a class for representing feed rows.

- rss._RssFeed eases accessing the row fields.
[rss] Add handling for 301 and 410 http responses.