FAQ inconsistent headers: fixed

FAQ "How do I post a challenge?": Added. Actually, the question added is "Can I post a challenge?" and for now for most people the answer is no. People I know (like, say, you) can be set as challenge adders. When the site goes live tell me if you'd like to be on that list.

funkiness about email address and "send challenges": The problem is that the system doesn't believe it's your email address until you've confirmed it. However, I let people check the "send challenges" box on signup. I'm still not sure how to finesse that, but for now I've changed the it from an error to a warning, so you can check the "send challenges" checkbox without a validated email. I also added a rather loud notice to the sidebar to let people know we're waiting for a confirmation, and what email we're waiting to confirm. That will also help people in the situation where they mistyped their email. The notice goes away after 24 hours if you don't confirm.