Added Swift Package Manager Support (#89)

* Added Swift Package Manager support

In order to make it work it is necessary to create a new Tag/Release for version 4.2.9 as it's specified in Line 5

* Update README.md

Package.swift

@@ -0,0 +1,31 @@
+// swift-tools-version:5.0
+//
+//  AFDateHelper.swift
+//  https://github.com/melvitax/DateHelper
+//  Version 4.2.9
+//
+//  Created by David Velarde on 6/7/19.
+//  Copyright (c) 2019. All rights reserved.
+//
+
+import PackageDescription
+
+let package = Package(
+    name: "DateHelper",
+    platforms: [
+        .iOS(.v9),
+        .macOS(.v10_11),
+        .tvOS(.v9),
+        .watchOS(.v2)
+    ],
+    products: [
+        .library(name: "DateHelper", targets: ["DateHelper"])
+    ],
+    targets: [
+        .target(
+            name: "DateHelper",
+            path: "Sources"
+        )
+    ],
+    swiftLanguageVersions: [.v5]
+)

README.md

@@ -406,7 +406,9 @@ Minimum: iOS 9, tvOS 9, watchOS 2, macOS 10.06
 
 ## Installation
 
-**Carthage** github "melvitax/DateHelper"  
+
+**Carthage** github "melvitax/DateHelper"
+**Swift Package Manager** https://github.com/melvitax/DateHelper.git
 **Cocoapods** pod 'AFDateHelper', '~> 4.3.0'  
 **Manually**  Include DateHelper.swift in your project