Improve the "contents" sidebar presentation.

[StevenDufresne]

Although I'm not 100% sure we need the content sidebar, at the very least, its layout is awkward. It's nested within the first three categories and has very little room to breathe.

Screenshot

[iandunn]

I feel like it's useful on longer pages, or even shorter ones, just to get an overview of what's there. Sometimes i open a page b/c it might have what i'm looking for, but then i can tell from the TOC that it doesn't and i move to the next tab.