This patch changes the HTML formatting (where to put newlines, etc...)
to better match commonmark's test cases. This has minimal effect of the
correctness of our markdown implementation, but makes it easier to test.
Changes:
- Use <em> instead of <i>.
- Newline before end of code block.
- <hr /> instead of <hr>.
- Newline before first list item.
- Newline between lines of a paragraph.
- Trim whitespace on lines of paragraphs.
Tests passed: 33/652 -> 87/652