Add support for "react-native link" (formerly rnpm link)

https://facebook.github.io/react-native/docs/linking-libraries-ios.html

Using `react-native link` seems to be the community standard for linking native libraries vs the projects current recommendation of using CocoaPods.

Is there a compatability issue or any other objection I'm not aware of that makes `react-native link` unusable?

If not, are there any plans already in place to transition over to using `react-native link`?

Thanks,
-- Arron