Update document_content.html

Change DocHub to Zeal.
fix bug 912084: Remap wiki URLs constructed via sumo.urlresolvers.reverse() for content zones

* Hack in sumo.urlresolvers.reverse() to apply URL remaps for wiki
  content zones

* Bug fix to constrain zone remaps per locale

* Tests
bug 912084: Cache wiki URL remap queries
Fix bug 920351 - Remove bold from current subnav
Fix bug 918111 - Add final homepage content
Merge pull request #1442 from Kapeli/master

Change DocHub to Zeal
Merge pull request #1448 from darkwing/subnav-bold-920351

Fix bug 920351 - Remove bold from current subnav
fix bug 921150 - Modify WYSIWYG scrolling behavior
Remove excessive heading space from homepage hacks headings
fix bug 920970 - Fix left column vertical alignment
Merge pull request #1447 from darkwing/homepage-edits-918111

Fix bug 918111 - Add final homepage content
Merge pull request #1450 from darkwing/scrolling-wysiwyg-921150-waffled

fix bug 921150 - Modify WYSIWYG scrolling behavior
Merge pull request #1451 from darkwing/home-hacks-headers

Remove excessive heading space from homepage hacks headings
Merge pull request #1452 from darkwing/zone-left-920970

fix bug 920970 - Fix left column vertical alignment
Merge pull request #1415 from lmorchard/912084-remap-wiki-url-construction

fix bug 912084: Remap wiki URLs constructed via sumo.urlresolvers.reverse() for content zones
Cleaning up the docs landing page /docs/
fix bug 922740 - Update wiki link for MDN testing
Merge pull request #1453 from darkwing/docs-landing-cleanup

Cleaning up the docs landing page /docs/
Merge pull request #1454 from darkwing/redesign-link-922740

fix bug 922740 - Update wiki link for MDN testing
Refactor page moving.

Rather than taking place immediately, and potentially breaking due to
excessive time required within a request/response cycle, page move is
now a Celery task. The user who requested the move will be notified
via email once the move is complete.

Page moves also now run in a transaction and only commit if
successful, and have more robust error catching and reporting. Errors
are logged, as well as being sent to the user who requested the move,
and in the case of unknown/unexpected errors, include the traceback
for diagnosis.