Print Cedar version number and git commit SHA when running specs if possible

- Works on Mac with dynamically-linked Cedar framework
- Works via CocoaPods, without git commit SHA
- iOS framework contains the version in its Info.plist, but can't print it when running

[#54066481]
Merge pull request #242 from pivotal-brian-croom/print-version-number

Print Cedar version number and git commit SHA when running specs