SuperCollider 3.6.6 with Emacs support (aka SCEL)

The current expression for SuperCollider in the repository builds and installs a version of the application which uses a built-in Qt-based IDE, but disables built-in support for using Emacs as an IDE.  This new expression enables that feature and also builds the built-in Qt IDE by default.  I used the current SuperCollider default.nix expression as a staring point, and then modified the proper cmake flag and added the necessary dependencies. 

Is there a best practice for providing end-users with simple documentation to configure Emacs to use this feature?

Some general background:
http://supercollider.github.io/
http://swiki.hfbk-hamburg.de/MusicTechnology/579

Thanks,
-Henry