Clean up input some more.

Use BeautifulSoup to clean up markup. This should fix dangling tags and the like. It operates on a
paragraph-by-paragraph basis.

Insert curly quotes. This currently doesn't handle prepended omission quotes properly (just 'cause)
but should be pretty nice otherwise.

Insert mdash and the like. This includes a fix to a particular encoding issue I've seen, and I'll
add more as I see them.

Some reformatting.