* Improve RSS entries for statuses

- Render polls in both accounts and tags serializers
- Refactor RSS serializers
- Change title preview to include ellipsis when truncated
- Change title preview to show CW instead of toot text
- Add tests

* Remove title from OEmbed serialization

Twitter doesn't serialize title either, and tihs allows us to move the
title formatting code to the RSS serializers.

for video player full screen button.

- Return all images as og:image
- Return videos as og:image (preview) and og:video
- Return profile:username on profiles

* Adjust status embeds

Adjust styles of embed code. Adjust styles of embed pages. Fix overflow of embed-modal.

* Remove trailing whitespace

* Using width from the variable

* Embed modal

* Proxy OEmbed requests from web UI

* Add close tag of iframe for oEmbed response

* add comma

- Use statuses controller for embeds instead of stream entries controller
- Prefer /@:username/:id/embed URL for embeds
- Use /@:username as author_url in OEmbed
- Add follow link to embeds which opens web intent in new window
- Use redis cache in development
- Cache entire embed

* Replace OEmbed Rabl template with serializer

* Replace initial state rabl with serializer