Add basic XML sitemaps using WWW::Sitemap::XML and WWW::SitemapIndex::XML.
Also add sitemap to robots.txt.
Fix bracket placement for usage(), copied from another script.
Don't delete .gitkeep, autoflush while building sitemaps.
Merge branch 'sitemaps' into beta

* sitemaps:
  Don't delete .gitkeep, autoflush while building sitemaps.
  Fix bracket placement for usage(), copied from another script.
  Also add sitemap to robots.txt.
  Add basic XML sitemaps using WWW::Sitemap::XML and WWW::SitemapIndex::XML.