Reorg pelican

This pull request reorganizes the NumFOCUS site completely. To see it rendered, visit http://dogwood.terrel.us 

The refactor includes:
- Better look and feel for the website
- Separation of pages and articles for editting
- Updated content in many pages
- Better navigation bar

There are still pages pending more content changes, but I think it is time to merge this work in and work on those pages separately.