Reduce app size

[mikew]

Built apps are ~14M. A good chunk of that is just swift:

$ du -shc Contents/Frameworks/*
236K	Contents/Frameworks/libswiftAppKit.dylib
6.2M	Contents/Frameworks/libswiftCore.dylib
 96K	Contents/Frameworks/libswiftCoreData.dylib
 40K	Contents/Frameworks/libswiftCoreFoundation.dylib
200K	Contents/Frameworks/libswiftCoreGraphics.dylib
 48K	Contents/Frameworks/libswiftCoreImage.dylib
104K	Contents/Frameworks/libswiftDarwin.dylib
340K	Contents/Frameworks/libswiftDispatch.dylib
2.9M	Contents/Frameworks/libswiftFoundation.dylib
 44K	Contents/Frameworks/libswiftIOKit.dylib
 92K	Contents/Frameworks/libswiftMetal.dylib
 60K	Contents/Frameworks/libswiftObjectiveC.dylib
 60K	Contents/Frameworks/libswiftQuartzCore.dylib
 44K	Contents/Frameworks/libswiftXPC.dylib
 76K	Contents/Frameworks/libswiftos.dylib
 11M	total

Although this project was started to learn Swift, maybe Objective-C would drastically reduce the final app sizes.