Added Dart implementation

Dart/xorencryption.dart

@@ -0,0 +1,20 @@
+
+String encryptDecrypt(String input) {
+  var key = ['K', 'C', 'Q']; //Can be any chars, and any size array
+  var output = [];
+  
+  for(var i = 0; i < input.length; i++) {
+    var charCode = input.codeUnitAt(i) ^ key[i % key.length].codeUnitAt(0);
+    output.add(new String.fromCharCode(charCode));
+  }
+  
+  return output.join("");
+}
+
+void main() {
+  String encrypted = encryptDecrypt("kylewbanks.com");
+  print("Encrypted:" + encrypted);
+  
+  String decrypted = encryptDecrypt(encrypted);
+  print("Decrypted:" + decrypted);
+}