Make it clearer which settings are required

Also, fix outdated counts of the number of settings.
Add a note about bleach and RSS
Bleach RSS feed content
Add an idea for testing
Documentation was missing a setting
Check that comments are hidden if no Disqus shortname is set
Add a note to release notes
Tidy up wording of TINYBLOG_NO_BLEACH description
Add a note about supported Python versions
Add a note about template integration
Version bump (not ready for release yet)
Properly <tt> a setting name
Fix capitalisation of HTML
Add tests to check validity of RSS feeds