Add a nanoc filter that runs HTML content through
[tidy-html](https://github.com/htacg/tidy-html5).
The content that is first run through ERB is often indented
incorrectly and inconsistently, and 'tidy' can fix that for us.
Rather than redirect /en/1/ to /en/al-fatihah/, render the surah
stream instead. A canonical `link` tag is included for the benefit
of search engines to differentiate between duplicates.
Preference is given to /en/al-fatihah/ over /en/1/.
