Introduce reading section with blog subscriptions

 - Introduce /reading section
 - Add /reading/subscriptions.xml OPML
 - Link to /reading from /more
Update blog subscriptions
Update Atom feed URL after FeedPress integration
Update blog subscriptions

 - Paul Graham's essays
 - Vinumeris blog
Work around FeedPress's default XSL

 - This approach requires a "Page Rule" at CloudFlare
 - This commit checks in FeedPress's atom.xsl exactly as it was
   originally downloaded, so as to track changes in subsequent commits.