Fix table rendering when lines are highlighted

[pborenstein]

Because of the way Prism renders Markdown tables, things get screwed up because the plugin expects that a \n ends the table line, so the markup wrappers end up in a strange place. Without highlighting, things look good, but with highlights, the spacing is all weird.

After hacking the Prism output a tad, things are better. We change <\/span>\n<\/span> to </span></span>\n