Add tasks for all the new languages

Task/Binary-search/Swift/binary-search-2.swift

@@ -0,0 +1,11 @@
+func binarySearch<T: Comparable>(xs: [T], x: T) -> Int? {
+  var (low, high) = (0, xs.count - 1)
+  while low <= high {
+    switch (low + high) / 2 {
+      case let mid where xs[mid] > x: high = mid - 1
+      case let mid where xs[mid] < x: low = mid + 1
+      case let mid: return mid
+    }
+  }
+  return nil
+}