Switch from "Related content" to "Browse similar content by category"
Reproduce self-promo section from homepage on content pages
Episode detail: change "Tagged with" to "Run time:"

The format of screencast headers is now the same on both listings and
detail pages, namely:

    title    | episode number
    run time | publication date
Article detail: remove "Tagged with"; move pubdate next to title
Fix encoding of code-blocks in #28
Add previous/next links on articles/screencasts