Django-bulbs

- Started `videos` app
- Added `SeriesDetailView` to `videos/views`

- Reduce RSS view caching from 10 to 5 min (per social squad)

- Fixed bugs with reading poll data for unpublished polls.
We were returning an error when sodahead reads failed.
We now return partial data.

- Add `bulbs/reading_list` application
Adding `bulbs.reading_list.mixins.ReadingListMixin` adds the reading list methods and properties
to a given object.

- Relocate `bulbs.content.models.ContentManager` to `bulbs.content.managers.ContentManager`

- Add common query methods to the `bulbs.content.models.ContentManager`
- evergreen: returning all Content with evergreen=True.
- evergreen_video: returning all Content with the configured VIDEO_DOC_TYPE document type.
- sponsored: returning all Content associated with a campaign.

- Add `pageview_client.clients.TrendingClient` popular logic to retrieve popular Content ids from
the service.

- Relocate `bulbs.special_coverage.search.SearchSlicer` to
`bulbs.reading_list.slicers.SearchSlicer`

- Add `bulbs.sections.managers.SectionIndexableManager` to retrieve sections by their percolator
identifier via elasticsearch

- Add `bulbs.sections.managers.SectionManager` to retrieve sections by their percolator
identifier via django

- Add `bulbs.special_coverage.managers.SpecialCoverage` to retrieve sections by their percolator
identifier via django

Polls

- Adds `bulbs/poll` application
Adding `"bulbs.poll"` to `INSTALLED_APPS` will
automatically add poll api routes to the `bulbs.api` routes

- Added `bulbs.poll.urls`
Adding `url(r'^', include('bulbs.poll.urls')),` creates a read-only
endpoint that exposes merged data from sodahead and our database.

It is accessible at `/poll/:poll_id/merged.json`

- Added `SODAHEAD_BASE_URL` to settings.
Most likely value is: `'https://onion.sodahead.com'`

- Added `SODAHEAD_TOKEN_VAULT_PATH` to settings.
In local/testing environments, this should be: `'sodahead/token'`
In production environments, this should be: `:property/sodahead/token`
ie: `starwipe/sodahead/token`.

In production, each app has it's own sodahead token, and all test
enviromnents share a sodahead token.

Vault

Vault is a credentials storage server:
<a href="https://www.vaultproject.io/">https://www.vaultproject.io/</a>

- Adds a vault client at: `bulbs.utils.vault`
`bulbs.utils.vault.read(path)` combines `VAULT_BASE_SECRET_PATH`
as a prefix to the passed in path and reads it from Vault.

- Adds vault test mocking at: `bulbs.utils.test.mock_vault`
See the implementation for documentation on mocking the vault in tests:
<a href="https://github.com/theonion/django-bulbs/blob/master/bulbs/utils/test/__init__.pyL131-L144">
https://github.com/theonion/django-bulbs/blob/master/bulbs/utils/test/__init__.pyL131-L144
</a>

- Added `VAULT_BASE_URL` to settings.
The base url of our Vault credentials store.
ie: 'http://hostname:8200/v1/'

- Added `VAULT_BASE_SECRET_PATH` to settings.
ie: `secrets/example`

- Added `VAULT_ACCESS_TOKEN` to settings.
ie: `very-secret-token`

- Remove redundant ES_URLS setting, just use ES_CONNECTIONS. Eventually all client projects can stop using ES_URLS too.
- Example app checks ELASTICSEARCH_HOST env variable (useful for using docker-based ES served inside VM)