title: Create a Timer using RxJava
body: <p>Currently I'm using a <code>CountDownTimer</code> that <strong>count down</strong> from a number and <code>onFinish</code> <strong>run an action</strong> and reset the timer, starting the count down from another number. </p>
  
  <p>For example inputs like this:</p>
  
  <pre><code>Remaining time = 13 | Interval = 30
  </code></pre>
  
  <p>Result in a output like this:</p>
  
  <pre><code>13 12 .. 3 2 1 0 30 29 .. 3 2 1 0 30 29 ...
  </code></pre>
  
  <p>I've tried to create a chain that generate the desired output using <code>interval</code>, <code>delay</code> and other <code>operators</code> but I'm yet to find a solution.</p>