Make tldr a more fully-featured sample.

- Render feed contents as HTML to eliminate "gremlins".
- Add "Read More" action item to invoke browser.
- Add "Share Article" action item to invoke bb.action.SHARE.
- "Read More" demonstrates one way to have a dynamic URI.
- "Share Article" demonstrates how to massage data for invocation.
  * Numeric entities (common in feeds) become proper UTF-8 characters.
  * UTF-8 data is properly encoded for invocation.
- Minor formatting changes, thanks to Momentics's Source->Format option.