title: Query arrays values with Firebase
body: <p>Is there any way to on Firebae to filter data in an array?</p>
  
  <p>I have this model on my Firebase:</p>
  
  <pre><code>-KABIGeWnBMUKjLTcvp8  
    deviceToken:"7DE60240CB4B712F05A009F32358610C1327917E7E68409..."
    favorites
      0:"Masha"
      1:"moksha"
    name:"juan"
  </code></pre>
  
  <p>And the problem is that I can't find any method to get all "users" that contain a certain value on the "favorites" array field.</p>