Add tasks for all the new languages

Task/Generator-Exponential/Swift/generator-exponential.swift

@@ -0,0 +1,47 @@
+func powGen(m: Int) -> GeneratorOf<Int> {
+  let power = Double(m)
+  var cur: Double = 0
+  return GeneratorOf { Int(pow(cur++, power)) }
+}
+
+var squares = powGen(2)
+var cubes = powGen(3)
+
+var nCube = cubes.next()
+
+var filteredSqs = GeneratorOf<Int> {
+  for var nSq = squares.next() ;; nCube = cubes.next() {
+    if nCube > nSq {
+      return nSq
+    } else if nCube == nSq {
+      nSq = squares.next()
+    }
+  }
+}
+
+extension GeneratorOf {
+  func drop(n: Int) -> GeneratorOf<T> {
+    var g = self
+    for _ in 0..<n {g.next()}
+    return GeneratorOf{g.next()}
+  }
+  func take(n: Int) -> GeneratorOf<T> {
+    var (i, g) = (0, self)
+    return GeneratorOf{++i > n ? nil : g.next()}
+  }
+}
+
+for num in filteredSqs.drop(20).take(10) {
+  print(num)
+}
+
+//529
+//576
+//625
+//676
+//784
+//841
+//900
+//961
+//1024
+//1089