markdown compound

md-blockquote-diff.md

Asciidoctor renders these two differently, causing the markdown version to be treated as a compound block quote with extra wrapping.

> I hold it that a little rebellion now and then is a good thing,
> and as necessary in the political world as storms in the physical.
> -- Thomas Jefferson, Papers of Thomas Jefferson: Volume 11

"I hold it that a little rebellion now and then is a good thing,
and as necessary in the political world as storms in the physical."
-- Thomas Jefferson, Papers of Thomas Jefferson: Volume 11

For now, I've decided that this doesn't seem desirable or worth the complexity to replicate in asciidork, so we render these the same way.