Merge pull request #560 from motocodeltd/master

swiftpm: set minimum target versions - allows deployment to watchos

Package.swift

@@ -3,12 +3,7 @@ import PackageDescription
 
 let package = Package(
     name: "SwiftyStoreKit",
-    platforms: [
-        .iOS(.v8),
-        .tvOS(.v9),
-        .watchOS("6.2"),
-        .macOS(.v10_10)
-    ],
+    platforms: [.iOS("8.0"), .macOS("10.10"), .tvOS("9.0"), .watchOS("6.2")],
     products: [
         // Products define the executables and libraries produced by a package, and make them visible to other packages.
         .library(