iphone 6 plus fixes

Fixes #294 and also added blank launch images so we display the editor in full 6+ glory with the demo app.

/cc @diegoreymendez 
The only change that I'd suggest is adding all these conditions inside a method like `isIPhoneSixPlus` or similar.  The reason is that putting these checks together in such a method would:

1. Allow for the creation of a shared iPhone6+ checking mechanism, eventually.
2. Make the code a bit easier to read.
3. Make the purpose of the conditions easier to fix, if we find we need to narrow them down, or change them.