Add tasks for all the new languages

Task/Arithmetic-Complex/Swift/arithmetic-complex-2.swift

@@ -0,0 +1,24 @@
+extension Complex : CustomStringConvertible {
+
+    public var description : String {
+
+        guard real != 0 || imaginary != 0 else { return "0" }
+
+        let rs : String = real != 0 ? "\(real)" : ""
+        let iS : String
+        let sign : String
+        let iSpace = real != 0 ? " " : ""
+        switch imaginary {
+        case let i where i < 0:
+            sign = "-"
+            iS = i == -1 ? "i" : "\(-i)i"
+        case let i where i > 0:
+            sign = real != 0 ? "+" : ""
+            iS = i == 1 ? "i" : "\(i)i"
+        default:
+            sign = ""
+            iS = ""
+        }
+        return "\(rs)\(iSpace)\(sign)\(iSpace)\(iS)"
+    }
+}