Django-bulbs

- Added Series Detail View to Videos App.

> *__This version safe to roll-out without changes to site.__*

- Added `target-host-channel` attribute to the `bulbs-video` element on the base special coverage landing page.

> *__This version safe to roll-out without changes to site.__*

- Changed css and html for special_coverage_landing

- Changed Instant Article `vault.read()`s to check for key of `authtoken` & throw an error if it's not present

- Removed 'FACEBOOK_API_ENV' in favor of boolean 'FACEBOOK_POST_TO_IA' for determining if article should be posted to IA or not
- Added `FACEBOOK_API_DEVELOPMENT_MODE` and `FACEBOOK_API_PUBLISH_ARTICLE` settings flags for instant article testing

- Added publishing to Facebook's Instant Article API on Content.save(), if the content feature type supports Instant Artices & the content is published.
- Added deletion from Facebook's Instant Article API on Content.save(), if the content has already been pushed to the Instant Article platform & is being unpublished
- Added deletion from Facebook's Instant Article API on Contnet.delete(), if the content had been pushed to the Instant Article platform