Add tasks for all the new languages

Task/Higher-order-functions/Swift/higher-order-functions-1.swift

@@ -0,0 +1,3 @@
+func func1(f: String->String) -> String { return f("a string") }
+func func2(s: String) -> String { return "func2 called with " + s }
+println(func1(func2)) // prints "func2 called with a string"

Task/Higher-order-functions/Swift/higher-order-functions-2.swift

@@ -0,0 +1,2 @@
+func func3<T>(f: (Int,Int)->T) -> T { return f(1, 2) }
+println(func3 {(x, y) in x + y}) // prints "3"