Change the minimum target for watchOS to 3.0 and fix #2.

Package.swift

@@ -8,7 +8,7 @@ let package = Package(
         .macOS(.v10_10),
         .iOS(.v10),
         .tvOS(.v9),
-        .watchOS(.v2)
+        .watchOS(.v3)
     ],
     products: [
         .library(name: "Dynamic", targets: ["Dynamic"])

Sources/Dynamic/Dynamic.swift

@@ -284,6 +284,9 @@ extension Dynamic {
     public var asCGAffineTransform: CGAffineTransform? { unwrap() }
     public var asUIEdgeInsets: UIEdgeInsets? { unwrap() }
     public var asUIOffset: UIOffset? { unwrap() }
+
+    #if !os(watchOS)
     public var asCATransform3D: CATransform3D? { unwrap() }
+    #endif
 }
 #endif