Fix bug 938005 - Display current time in profile user's timezone

When displaying a user's profile, show the current time in their timezone.

If the logged-in user's timezone is different from the profiled user, provide a tooltip that tells how many hours ahead or behind the profiled user's timezone is from the logged-in user's.

Bug 938005 comment 2 suggested that we could get the current user's timezone from the browser even if they're not logged in or have not set a timezone in their profile, but it wasn't clear to me how we could do that without a bit of inline javascript in our template, which the mozillians.org security settings won't execute.