Added swift package and carthage information

Author: Wes Billman

Package.swift

@@ -0,0 +1,6 @@
+import PackageDescription
+
+let package = Package(
+    name: "JSONFeed",
+    exclude: ["JSONFeed.xcodeproj", "JSONFeedTests", ".travis.yml", "codecov.yml", ".swiftlint.yml"]
+)

README.md

@@ -1,6 +1,37 @@
 [![Build Status](https://travis-ci.org/wesbillman/JSONFeed.svg?branch=master)](https://travis-ci.org/wesbillman/JSONFeed)
 [![Codecov](https://img.shields.io/codecov/c/github/wesbillman/JSONFeed.svg)](https://codecov.io/gh/wesbillman/JSONFeed)
+[![Carthage compatible](https://img.shields.io/badge/Carthage-compatible-4BC51D.svg?style=flat)](https://github.com/Carthage/Carthage)
+![SwiftPM Compatible](https://img.shields.io/badge/SwiftPM-Compatible-brightgreen.svg)
 
 ### JSONFeed
 
 Swift parsing for [JSON Feed](https://jsonfeed.org/)
+
+## Installation
+
+### Carthage
+
+You can install [Carthage](https://github.com/Carthage/Carthage) with [Homebrew](http://brew.sh/) using the following command:
+
+```bash
+brew update
+brew install carthage
+```
+To integrate JSONFeed into your Xcode project using Carthage, specify it in your `Cartfile` where `"x.x.x"` is the current release:
+
+```ogdl
+github "wesbillman/JSONFeed" "x.x.x"
+```
+
+### Swift Package Manager
+
+To install using [Swift Package Manager](https://swift.org/package-manager/) have your Swift package set up, and add JSONFeed as a dependency to your `Package.swift`.
+
+```swift
+dependencies: [
+    .Package(url: "https://github.com/wesbillman/JSONFeed.git", majorVersion: 0)
+]
+```
+
+### Manually
+Add all the files from `JSONFeed/JSONFeed` to your project