title: string.includes('a') function not defined in Node.js 0.12?
body: <p>I do understand the includes() array-function is only supported for ECMAscript 6+, but isn't ECMAscript 6 now already supported in Node.js? I've also tried to run:</p>
  
  <pre><code>node --harmony app.js
  </code></pre>
  
  <p>but that gave me an:</p>
  
  <pre><code>node: bad option: --harmony
  </code></pre>
  
  <p>On my Windows 8 machine.</p>
  
  <p>I've also tried to use string.contains('a'); but that array-function isn't defined as well.</p>