* add `generator` property
* add image property
* use `xml_escape` instead of `![CDATA]`
* use `date_to_rfc822` instead of the date format string (thanks @troyswanson!)
* fix self reference url
* switch to `isPermaLink` for the `guid`
This is the big site redesign by @cobyism. To work with the new
site deployment mechanism, it is being copied from the gh-pages
branch of that PR into the existing site dir. Before we finally
deploy the new site, we should remember to merge #583 so that we
keep all the history from that PR.