Add TwoPaneRight Layout

[TypicalFence]

Closes https://github.com/ianyh/Amethyst/issues/1216

I'd like to add it as a native layout because custom layouts do not support the native shrink/expand commands.

Getting xcode to work was quite the hassle, I've used an older version of xcode, but will update for future PR's. I hope this is somehow mergeable as the xcode project files are confusing to me.

The changes to the podfile were needed for some reason because it wouldn't install the linter otherwise. Can't tell if this is a me problem or a general one. So maybe those changes should be removed?