title: How to make one Observable sequence wait for another to complete before emitting?
body: <p>Say I have an <code>Observable</code>, like so:</p>
  
  <pre><code>var one = someObservable.take(1);
  
  one.subscribe(function(){ /* do something */ });
  </code></pre>
  
  <p>Then, I have a second <code>Observable</code>:</p>
  
  <pre><code>var two = someOtherObservable.take(1);
  </code></pre>
  
  <p>Now, I want to <code>subscribe()</code> to <code>two</code>, but I want to make sure that <code>one</code> has completed before the <code>two</code> subscriber is fired.</p>
  
  <p>What kind of buffering method can I use on <code>two</code> to make the second one wait for the first one to be completed?</p>
  
  <p>I suppose I am looking to pause <code>two</code> until <code>one</code> is complete.</p>