[bug 928901] Fixed Needs Attention filter

It should filter by updated in the last 7 days, instead of created.
Otherwise, recent replies will get lost for older questions.
Fix import of get_auth_str for celery.
[bug 950759] Limit auto-escalation to questions with no replies.
[bug 943370] Fix subscribe button text.
Move tabzilla.js loading further down and add async.
[Bug 943397] Add l10n warnings to FxOS articles.
[bug 943364] L10n Dashboard: Simplify overview table.

* Remove navigation breakout
* Include all categories in the All KB Articles row
[bug 943364] L10n Dashboard: Remove readouts no longer desired.

* Only keep the All/Most Visited, Templates and Unreviewed
Remove unused imports in wiki/cron.py
Update django-tidings to master tip.

Includes schematic migration to add tidings to South.