官网：
https://swift.org/
https://developer.apple.com/swift/
GitHub：
https://github.com/apple/swift
http://numbbbbb.gitbooks.io/-the-swift-programming-language-/content/chapter1/02_a_swift_tour.html
http://numbbbbb.gitbooks.io/-the-swift-programming-language-/
http://wiki.jikexueyuan.com/project/swift/
https://github.com/numbbbbb/the-swift-programming-language-in-chinese
https://github.com/ipader/SwiftGuide
http://segmentfault.com/a/1190000000533936
http://swifter.tips/lazy/
http://www.jianshu.com/p/449cfe1b8fbb
http://swifteducation.github.io/
http://swift.gg/
http://swift-lang.org/main/
http://www.swiftguide.cn/
http://alisoftware.github.io/swift/2015/09/06/thinking-in-swift-1/
http://alisoftware.github.io/swift/2015/09/20/thinking-in-swift-2/
http://alisoftware.github.io/swift/2015/10/03/thinking-in-swift-3/
http://alisoftware.github.io/swift/2015/10/11/thinking-in-swift-4/
