title: SignalFX detector data().count() based on condition
body: <p>Is it possible to implement count() MTS based on condition?</p>
  <p>For instance:
  We need to monitor the amount of time RDS CPU picks the point of 95% for the last 3 days.</p>
  <pre><code>A = data('CPU_Utilization').count(...when point &gt; 95%). 
  detector(when(A &gt; {number_of_times_breached}, lasting='3d')).publish(...)
  </code></pre>
  <p>Update.</p>
  <p>Solution was found by my colleague:</p>
  <pre><code>A = data('CPU_Utilization').above({condition_value}, inclusive=True).count(...)
  </code></pre>