Re-encode questions as utf-8.

That's what it claims to be, so that's what it should be. This means
answers no longer get cut off at the first non-ascii character. Only the
one question file needed re-encoding.
Fix two questions.

I don't particularly like the new version of the commuting workers one,
it's awkward. But at least it's... maybe not totally unambiguous,
because it might mean "which state has a greater percentage of the total
pool of people commuting to work by public transportation", but I think
that's an unlikely reading.