Add beta version info to README

Author: mafinar-cmb

README.md

@@ -2,6 +2,8 @@
 
 [![Build Status](https://travis-ci.com/code-shoily/algorithms-in-dart.svg?branch=master)](https://travis-ci.com/code-shoily/algorithms-in-dart)
 
+##### This currently uses the beta version of Dart
+
 Implementation of several algorithms with Dart programming language.
 
 I will be implementing algorithms (In random order, perhaps) with Dart as I am learning this simple language. This readme will be updated with each implementation.