Statify and curate the overview of guides

Right now a Jekyll upgrade on GitHub has broken
the page. The first commit tries to alleviate this
by creating a cleaner, static markdown version of
the page.

The subsequent commits reorder and categorize the content.
There's also

```
    * [Macro Annotations](/overviews/macros/annotations.html)
    * [Macro Paradise](/overviews/macros/paradise.html)
    * [Roadmap](/overviews/macros/roadmap.html)
    * [Changes in 2.11](/overviews/macros/changelog211.html)
```