title: ElastAlert - override run_every in config.yaml
body: <p>Is it possible to override the <code>run_every</code> attribute in the config.yaml?</p>
  
  <p>Basically I have a <code>config.yaml</code> that has the following line:</p>
  
  <pre><code>run_every:
      seconds: 30
  </code></pre>
  
  <p>Now I have five rules that are using this <code>config.yaml</code>.  So all of them are running every 30 seconds.  On the fifth rule I want to run every 60 seconds however if I put the following line in my <code>fifth-rule.yaml</code>:</p>
  
  <pre><code>run_every:
      seconds: 60
  </code></pre>
  
  <p>It still runs every 30 seconds.  Any thoughts?</p>