Add schema.org VideoObject RDFa metadata

* Update video.html: http://schema.org/VideoObject
* Add duration_iso8601 filter and tests
* Add duration_iso8601 filter and tests
* Updated test_filters.py: PEP8
* Updated video.html: next <meta> in <dd>
* Removed explicit Python tag
* Updated video.html: Added v.category.title tag
* Updated video.html: Added sameAs v.get_absolute_url
* Updated video.html: <meta content=> -> <link href=>

See https://github.com/willkg/richard/pull/213
Add Wes Turner and Paul Collins to AUTHORS
Fix typo in hacking docs