Improve fix from 098369b33f694becf53fcdd9535c631e3f18a062.

Remove extra newlines which aren't needed.
Simplify license.html.

Remove the custom `replace` filter and use `markdownify` instead.
Revert 26bb900113ad6385c743b7a6d61c5595364d075b.

Jekyll already takes care of those.
Simplify quotes and apostrophes.