* Raise an error for remote url in StatusFinder

Previous implementation had allowed remote url with status id which also exists on local.

Then that bug leads /api/web/embed to return wrong embed url.

* Fix oembed_controller_spec

- 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

* Add StreamEntryFinder class to parse URLs

* Use StreamEntryFinder and clean up api/oembed controller