Notifun shouldn't use styles from project it's included into.

It should have its own like how Sidekiq's dashboard is completely its own thing. Have a layout that includes the notifun sass. I think a controller structure like Devise's would work well.
https://github.com/plataformatec/devise/tree/master/app/controllers

A top level NotifunController that specifies the layout (and anything else) and subclasses the parent as specified in the config, then the individual ones subclass it so they all get the layout and any shared methods.