navigation to item details renders twice on Android

[DavyDeDurpel]

If you look closely you can see it in your example. You briefly see the navigation card of the item details view appearing with the right button icon in it and at the end it's no longer visible.

If you put a console.log() inside the _renderRightComponent function, you will see that the function gets called 4 times when clicking on any of the Items.

I can't provide you with a patch (yet) as I'm very new to React and React Native ;-)

[sausaw]

I can reproduce this but coudn't figure out where the icon on the right comes from

[sausaw]

Fixed in #11