add featured article and create a dashboard box on homepage, fixes #24

[mireille-raad]

Currently the homepage has nothing under "learn more" and the dashboard-y thing for CPython compatibility is at the end of a long text.

This PR re-arranges the content, so it looks like this:

The content is generated by:

• checking posts with a featured category for the featured box. I set a limit of 3 (optimism 101)
• reading from the _configh.yml file for whatever other dashboard pages we might build

dashboards:
  - title: CPython test compatibility 
    url: /pages/regression-tests-results.html