Fix matching of endblocks, use `:norm!`

`{% endblock foo %}` is valid for Django, and wasn't matched before.
This also adds a comma after `cache` for b:match_words.
match_words: add `verbatim`, `empty` (with `for`), sort
Merge pull request #7 from blueyed/fix-endblocks-etc

Fix matching of endblocks, use `:norm!`