Update README

Author: a2

README.md

@@ -1,12 +1,12 @@
 MessagePack.swift
 =================
 
-[![CI Status](http://img.shields.io/travis/a2/MessagePack.swift.svg?style=flat)](https://travis-ci.org/a2/MessagePack.swift)
+[![CI Status](https://img.shields.io/travis/a2/MessagePack.swift.svg?style=flat)](https://travis-ci.org/a2/MessagePack.swift)
 [![Version](https://img.shields.io/cocoapods/v/MessagePack.swift.svg?style=flat)](http://cocoapods.org/pods/MessagePack.swift)
 [![License](https://img.shields.io/cocoapods/l/MessagePack.swift.svg?style=flat)](http://cocoapods.org/pods/MessagePack.swift)
 [![Platform](https://img.shields.io/cocoapods/p/MessagePack.swift.svg?style=flat)](http://cocoapods.org/pods/MessagePack.swift)
 
-A fast, zero-dependency MessagePack implementation written in Swift 3. Supports Apple platforms and Linux.
+A fast, zero-dependency MessagePack implementation written in Swift 4. Supports Apple platforms and Linux.
 
 ## Installation
 
@@ -15,15 +15,15 @@ A fast, zero-dependency MessagePack implementation written in Swift 3. Supports
 To use CocoaPods, add the following to your Podfile:
 
 ```ruby
-pod 'MessagePack.swift', '~> 2.1.0'
+pod 'MessagePack.swift', '~> 3.0'
 ```
 
 ### Carthage
 
 To use Carthage, add the following to your Cartfile:
 
 ```ogdl
-github "a2/MessagePack.swift" >= 2.1.0
+github "a2/MessagePack.swift" ~> 3.0
 ```
 
 ### SPM (Swift Package Manager)
@@ -36,14 +36,16 @@ import PackageDescription
 let package = Package(
     name: "MyAwesomeApp",
     dependencies: [
-        .Package(url: "https://github.com/a2/MessagePack.swift.git", majorVersion: 2, minor: 1),
+        .Package(url: "https://github.com/a2/MessagePack.swift.git", majorVersion: 3),
     ]
 )
 ```
 
 ## Version
 
-2.x supports Swift 3. Support for Swift 2 was dropped after [1.2.0](https://github.com/a2/MessagePack.swift/releases/tag/1.2.0).
+- Versions 3.x support Swift 4.
+- Support for Swift 3 was dropped after [2.1.1](https://github.com/a2/MessagePack.swift/releases/tag/2.1.1).
+- Support for Swift 2 was dropped after [1.2.0](https://github.com/a2/MessagePack.swift/releases/tag/1.2.0).
 
 ## Authors