Release 2.2.2:
- fix: remove the beginning and ending spaces in contents of xml
  nodes, but do not collapse spaces inside PCData. (by C. Troestler)

Release 2.2.1:
- fix: do not set default namespace in final rss
- fix: rdf parsing
- fix: Rss.sort_items_by_date sorts with old items last, as documented

Release 2.2.0:
- add: Rss.compare_item
- fix: provide polymorphic functions on channel_t and on item_t
- add: Rss.channel_t_of_xmls
- add: Rss.xml_of_source
- fix #5: incorrect sort

Release 2.1.0:
- handle namespaces (the list is stored in the channel structure)
- allow the library user to read addition information from
  <item> and <channel> prefixed subnodes, as the RSS 2.0 specification
  indicates this is the way to extend RSS information
- handle cloud, skipHours, skipDays, picsRating in Channel
- use Neturl.url instead of sting
- use Netdate instead of Rss_date, which was a copy of Netdate
- default encoding is now UTF-8
- new parameter "indent" for printing
- new "opts" parameter when reading
- reading returns error list besides channel
