title: Emit a single value
body: <p>I would like to emit a single value. </p>
  
  <p>According to this <a href="https://gist.github.com/staltz/868e7e9bc2a7b8c1f754">post</a>, the following should be valid:</p>
  
  <pre><code>var requestStream = Rx.Observable.just('https://api.github.com/users');
  </code></pre>
  
  <p>However, this does not work. <code>just</code> is not defined.</p>
  
  <p>Has it been deprecated? Is there something that I can use instead?</p>