Fix ARC compile errors in a way that is compatible with non-ARC builds

[slessard]

Added ARCMacros.h to enable building the project both with and without ARC support.

[jklp]

Hi, thanks for the pull request though unfortunately it looks like DCIntrospect is no longer maintained. Good news though, myself and @logicreative have decided to revive DCIntrospect, and created a fork at https://github.com/logicreative/DCIntrospect-ARC to hopefully merge all pull requests and forks back into a single repo.

If you don't mind sending your pull request to the DCIntrospect-ARC repo, we'll try and merge it as quickly as possible. We're also going to be more active with the CocoaPods package manager, so we'll update the latest CocoaPod's podspect once all changes have been merged.

Thanks Jerrold