Add DTD information
More versatile detection of <channel> for RSS2
Filter out prefixed tags for RSS2
Fix parsing of timezone for RSS2
Atom: allow empty subtitles
RSS2: allow the day of the week not to be present in dates
RSS2: allow channel/description to be empty
Export an XML module
Atom: allow content to be (X)HTML

Fixes https://github.com/Cumulus/Syndic/issues/20
Atom: adjust the unsafe representation for XML content
Atom: allow [summary] to be XHTML
Fix the documentation of [parse] functions
RSS2: take appropriate action when some data is missing
RSS2: be even more flexible with date parsing