Add universal architecture compatibility

This could be added to your pull request to the original Square repo or I can submit it once yours is merged.

The commit details:

This updates the default target architecture to standard
(combined i386 and x86_64) and fixes compilation errors when
targetting i386. See:

http://stackoverflow.com/questions/7110245/error-building-32-bit-os-x-app

..for details on the compilation errors with synthesized properties
requiring explicit instance variables.