[WIP] ARC and modern Objective-C

:rotating_light: not ready to merge :rotating_light:

I've tried to start on #54 but I'm stumped on an issue that occurred.

`- test_isGoing` in AsynchronousTestingTest.m fails because, from what I can gather, the matcher's reference to `foo` is not updated after it's modified in the block and copied to the heap.

I'm thinking it could be the varargs in `_EXPObjectify` that trips up ARC so I'll investigate that next but if anyone has some ideas, I'd be happy to hear them.