Implement "requiresMainQueueSetup"

[mcrowe]

React Native now requires that this library implements requiresMainQueueSetup, as described in this YellowBox deprecation warning.

[michaelkoelewijn]

Due to IOS 13 needing a main thread setup which this package currently lacks, we have decided to fork the project and add the necessary changes (including the removal of this warning).
I have created a PR but due to inactivity in this project i'm afraid it will not get merged any time soon.

#20

[EricWiener]

@michaelkoelewijn thanks for making a fork. Your version works great.