Currently only support soundcloud (futur providers will be add)

Use SoundCloud Oembed API https://developers.soundcloud.com/docs/api/reference#oembed in order to support more links

Currently does not support *group* embed widget (like https://soundcloud.com/groups/made-with-ableton-live)

Encapsulate spotify integration inside rocketchat:spotify package. No more inside rocketchat:oembed.

Remove rocketchat:spotify from default list of packages inside `.meteor/{packages,version}`

- https://open.spotify.com/track/34AWo71Ya5gq7wpNnatwr7
- spotify:track:34AWo71Ya5gq7wpNnatwr7

Works with tracks, albums, artists and playlists.

Improve layout of oembed url and add omebeds to the end of the message instead replace link with oembed

Suggested by @rodrigok.

Looks much better on small images to be aligned in the center.  Especially if height needs to remain at 200px;

This way area doesn't expand after the image loads causing content to shift.

By setting height to 200 you were causing images to stretch.  Setting it to a max-height, makes it fit auto resize to fit your max height.