Add tasks for all the new languages

Task/Balanced-brackets/Swift/balanced-brackets-3.swift

@@ -0,0 +1,13 @@
+func randBrack(n: Int) -> String {
+
+  var bracks: [Character] = Array(Repeat(count: n, repeatedValue: "["))
+
+  for i in UInt32(n+1)...UInt32(n + n) {
+
+    bracks.insert("]", atIndex: Int(arc4random_uniform(i)))
+
+  }
+
+  return String(bracks)
+
+}