Add tasks for all the new languages

Task/Delegates/Swift/delegates-2.swift

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+protocol Thingable : class {
+  func thing() -> String
+}
+
+class Delegator {
+  weak var delegate: Thingable?
+  func operation() -> String {
+    if let d = self.delegate {
+      return d.thing()
+    } else {
+      return "default implementation"
+    }
+  }
+}
+
+class Delegate : Thingable {
+  func thing() -> String { return "delegate implementation" }
+}
+
+// Without a delegate:
+let a = Delegator()
+println(a.operation())    // prints "default implementation"
+
+// With a delegate:
+let d = Delegate()
+a.delegate = d
+println(a.operation())    // prints "delegate implementation"