title: How to tell the version number of RxJS
body: <p>How to tell the version of the installed RxJS from the code? For example:</p>
  
  <pre><code>var Rx = require('rxjs/Rx');
  console.log(Rx.rev);   // undefined
  console.log(Rx.version);  // undefined
  </code></pre>
  
  <p>Second question: How to tell if it's rxjs5 ?</p>