Removed __attribute__((NSObject)) from the dispatch_queue_t property.

Using Xcode 5.1 it seems that the __attribute__((NSObject)) is no longer necessary for dispatch_queue_t properties.

The compiler (LLVM 5.1) was complaining about the "@property (nonatomic, strong) __attribute__((NSObject)) dispatch_queue_t captureQueue" in the ZXCapture, saying that "__attribute__((NSObject)) is for pointer types only".

Removing it, seems to have fixed the issue.

Thanks.