This closes issue #10, in theory, but I'm not completely happy with the
behavior. The output for both UTF-8 and ISO-8859-1 sources is arguably
correct, but I think it'd be better to do some autodetecting of the file
encoding, and explicitly convert everything to UTF-8 on input. One
option is the [`chardet` gem][gem], but I'm loath to add another
dependency to Rocco...
[gem]: http://rubygems.org/gems/chardet/versions/0.9.0
