Added support for embedded radd.it playlists.

Self-contained in its own function, added support to embed in-line radd.it links.
I can't add commits, but this regex should do the trick: `/^https?:\/\/(?:(?:www|m|embed)\.)?radd\.it([\w\/_]+)/i`

Or, if `earl` *must* start with `/r/`, this: `/^https?:\/\/(?:(?:www|m|embed)\.)?radd\.it(\/r\/[\w_]+)/i`