OS X El Capitan no sound output device found
The very first thing I would do is run an Apple Hardware Test.

When you turn on the computer, before you hear the startup chime, press and hold the D key.

Also, there is one item to double check and that is if you uninstalled Soundflower completely.

Use an app like  AppCleaner to ensure that you've got everything associated with the app.  Best of all, it's free.