Move to XCTest

This change moves over to XCTest and moves over to using schemes for building/testing.
It also cleans up a pile of warnings throughout the project, and simplifies the project by consolidating build options.
This allows us to compile without analyzer warnings on Xcode 5 and 6. Tested building 32/64 on Xcode 5 and 6.
All tests currently pass.
I thought Apple documentation (plus tvl recommendation) states that %zd was for signed types and %tu was for unsigned types?

https://developer.apple.com/library/mac/documentation/Cocoa/Conceptual/Strings/Articles/formatSpecifiers.html