Add tasks for all the new languages

Task/Run-length-encoding/Swift/run-length-encoding-3.swift

@@ -0,0 +1,15 @@
+// "3W1B2W" -> "WWWBWW"
+func decode(encoded: String) -> String {
+    let scanner = NSScanner(string: encoded)
+    var char: NSString? = nil
+    var count: Int = 0
+    var out = ""
+
+    while scanner.scanInteger(&count) {
+        while scanner.scanCharactersFromSet(NSCharacterSet.letterCharacterSet(), intoString: &char) {
+            out += String(count: count, repeatedValue: Character(char as! String))
+        }
+    }
+
+    return out
+}