Add SoundCloud embedding

Works on urls like:
- soundcloud.com/:username
- soundcloud.com/:username/:track
- soundcloud.com/:username/sets/:playlist
- soundcloud.com/groups/groupName
Return a jquery object from the mediamessage handler

Avoids 'reaching' outside where this method should be reaching.
Merge pull request #640 from spadgos/soundcloud-embed

Add SoundCloud embedding