参考链接：https://github.com/CocoaLumberjack/CocoaLumberjack
Xcode8.0版本需要设为3.2
Xcode7.2版本需要设为2.2.0
Backwards compability
- for iOS 5 and OS X 10.7, use the 3.3 version
- for Xcode 8 and Swift 3, use the 3.2 version（这里）
- for Xcode 7.3 and Swift 2.3, use the 2.4.0 version
- for Xcode 7.3 and Swift 2.2, use the 2.3.0 version
- for Xcode 7.2 and 7.1, use the 2.2.0 version（这里）
- for Xcode 7.0 or earlier, use the 2.1.0 version
- for Xcode 6 or earlier, use the 2.0.x version
- for OS X < 10.7 support, use the 1.6.0 version