Xcode 5.1 Support

- Bumps Objective Git to https://github.com/libgit2/objective-git/commit/d9965ae967845a56ef0401b89de2bfb0383f8832
- Validates Git!'s project settings
- Don't use hard linked paths 
- Target `ObjectiveGit-iOS` instead of `ObjectiveGit-iOS-arm64`