3467 FAQ caution, notice, and example styles

https://code.google.com/p/otwarchive/issues/detail?id=3467

Styles for the FAQ pages, specifically requested by wranglers for wrangling guidelines. Rebase of pull request #1049, with a tweak to the .example selector (there's no flash notice with an "example" class -- actually, fun fact, there is nothing else on the archive with that class -- so we don't have to use a .userstuff class).

(The .tweet_list style that got clobbered is from the old Twitter widget and just didn't get removed. Sob, I miss you, old Twitter widget.)