This will make it easier in the future to test that we support labels,
and it tells people who are looking to confirm that we support labels
that we in fact do.
This fixes some bugs that were present in the old Prettify highlighter
when there was a mix of JavaScript and HTML in the same code block. Now
with Rouge, the highlighter used by Jekyll, these cases are properly
handled and HTML no longer looks strange.
This does not convert all of the code blocks over, because there are
still some code blocks which double as the actual JavaScript code
powering the example that need to be migrated.
