Made SENTRY_DSN optional to prevent it from raising misleading exceptions.

Fixes #1900.
vagrant: globally configure npm to ignore expired SSL certs
Merge pull request #1902 from jezdez/fix-sentry-settings

Made SENTRY_DSN optional to prevent it from raising misleading exceptions.
Specify a specific version of the Sphinx theme to trigger a proper rebuild on RTD.
Merge pull request #1903 from lmorchard/npm-no-strict-ssl

vagrant: globally configure npm to ignore expired SSL certs
Revert "bug 773522: Follow up with previous djcelery migration fix, returns control of migrations to app itself"

This reverts commit 368d9d74473a75844939494986ff4472d55d1ee1.
Merge pull request #1908 from lmorchard/djcelery-migration-fix

Resolve djcelery migration error in Vagrant
vagrant: Disable broken migration that prevents tidings migration from executing
Merge pull request #1911 from lmorchard/fix-tidings-migration

vagrant: Disable broken migration that prevents tidings migration from executing
Change edit button label to simply "Edit"

Based on the following A/B test results:
http://optimize.ly/~VoAkCt?token=20ca22118554616e752d

The label "Edit Page" is used elsewhere (like on profile pages and in
the revision dashboard) but these instances are intentionally left
unchanged. Only on article pages is "Page" clear from context.
Merge pull request #1912 from openjck/edit-button-text

Change edit button label to simply "Edit"
Remove redesign banner
Merge pull request #1913 from openjck/remove-redesign-banner

Remove redesign banner
Fix #1782: Delete page templates from old design
Merge pull request #1792 from openjck/migrate-redesign-templates

Fix #1782: Delete page templates from old design