Use correct slidy string for conversion tests
Use correct slidy string for conversion tests

Similar to [the dzslides test fix][1], the order of attributes does not
match Pandoc output. Also, IDs must be unique.

[1]: https://github.com/changecase/pandoc-ruby/commit/8c4ce11557510139b558609e883c3789f30d12d7

dalehamel/ruby-pandoc,alphabetum/pandoc-ruby,alphabetum/pandoc-ruby