[RubyMotion] Specify the Realm framework as a framework instead.

Thanks to @alloy for this fix. I've confirmed it works locally. Original PR here #1037, but couldn't be merged directly because CLA.

Fixes #981.

![image](https://cloud.githubusercontent.com/assets/474794/4684107/3423529c-562d-11e4-8716-3069c86ae841.png)