Fix duplicate entries on Franchise tab

Related thread: http://forums.hummingbird.me/t/clicking-on-an-anime-on-the-franchise-page/17174

Seems the update to ember-data beta11 introduced this bug.

![](http://cl.ly/image/3w0p2w0V2z0g/Image%202014-11-02%20at%208.45.01%20am.png)

Was leaking FullAnime entries into the franchise relationship for some reason, the added inverse option fixes it.