Adjust ordering options for returned results.
Add .locales property to PageDB.
Rewrite html_extractor using Gumbo HTML5 parser instead of html5lib.
Fold walk_gumbo and _process_element into _process_document.

MOAR SPEED.

(Also a couple of bugfixes.)
Merge pull request #2 from zackw/master

Adjust ordering options for returned results.