Refactor project to support SPM

.gitignore

@@ -157,3 +157,16 @@ Icon
 Network Trash Folder
 Temporary Items
 .apdisk
+
+# Created by https://www.gitignore.io/api/swiftpackagemanager
+# Edit at https://www.gitignore.io/?templates=swiftpackagemanager
+
+### SwiftPackageManager ###
+Packages
+.build/
+xcuserdata
+DerivedData/
+*.xcodeproj
+
+
+# End of https://www.gitignore.io/api/swiftpackagemanager

Package.resolved

@@ -0,0 +1,43 @@
+{
+  "object": {
+    "pins": [
+      {
+        "package": "CwlCatchException",
+        "repositoryURL": "https://github.com/mattgallagher/CwlCatchException.git",
+        "state": {
+          "branch": null,
+          "revision": "7cd2f8cacc4d22f21bc0b2309c3b18acf7957b66",
+          "version": "1.2.0"
+        }
+      },
+      {
+        "package": "CwlPreconditionTesting",
+        "repositoryURL": "https://github.com/mattgallagher/CwlPreconditionTesting.git",
+        "state": {
+          "branch": null,
+          "revision": "c228db5d2ad1b01ebc84435e823e6cca4e3db98b",
+          "version": "1.2.0"
+        }
+      },
+      {
+        "package": "Nimble",
+        "repositoryURL": "https://github.com/Quick/Nimble",
+        "state": {
+          "branch": null,
+          "revision": "b02b00b30b6353632aa4a5fb6124f8147f7140c0",
+          "version": "8.0.5"
+        }
+      },
+      {
+        "package": "Quick",
+        "repositoryURL": "https://github.com/Quick/Quick",
+        "state": {
+          "branch": null,
+          "revision": "33682c2f6230c60614861dfc61df267e11a1602f",
+          "version": "2.2.0"
+        }
+      }
+    ]
+  },
+  "version": 1
+}

Package.swift

@@ -0,0 +1,27 @@
+// swift-tools-version:5.1
+// The swift-tools-version declares the minimum version of Swift required to build this package.
+
+import PackageDescription
+
+let package = Package(
+    name: "Resolver",
+    products: [
+        .library(
+            name: "Resolver",
+            targets: ["Resolver"]
+        ),
+    ],
+    dependencies: [
+        .package(url: "https://github.com/Quick/Quick", from: "2.2.0"),
+        .package(url: "https://github.com/Quick/Nimble", from: "8.0.0"),
+    ],
+    targets: [
+        .target(
+            name: "Resolver"
+        ),
+        .testTarget(
+            name: "ResolverTests",
+            dependencies: ["Resolver", "Quick", "Nimble"]
+        ),
+    ]
+)