Added support for swift package manager

Author: jayhickey

Package.swift

@@ -0,0 +1,22 @@
+// swift-tools-version:4.0
+
+import PackageDescription
+
+let package = Package(
+    name: "ReSwift-Router",
+    products: [
+      .executable(name: "ReSwift-Router", targets: ["ReSwiftRouter"]),
+    ],
+    dependencies: [
+      .package(url: "https://github.com/ReSwift/ReSwift", .upToNextMajor(from: "4.0.1"))
+    ],
+    targets: [
+      .target(
+        name: "ReSwiftRouter",
+        dependencies: [
+          "ReSwift"
+        ], 
+        path: "ReSwiftRouter"
+      )
+    ]
+)