Fix a number of validation/style errors:

 * <pre> is not allowed to be nested inside of <p> elements in HTML
 * Indentation of </p> doesn't match corresponding <p>
 * <p> element not explicitly closed
 * One more </div> than <div>

In each case, the template was fixed to match how a HTML5 parser would "see"
the resulting page.
Merge pull request #8702 from rubys/master

Fix a number of validation/style errors