title: Searchkick - ranges on 2 separate columns
body: <p>I'm trying to create multiple ranges with 2 columns. I know multiple ranges can be achieved but I need it to work with 2 columns.</p>
  <p>In my model I have a <code>min_age</code> and <code>max_age</code>. The user can select multiple ages to filter from, for example: the options are <em>10,11,12,13,14,15,16,17,18</em> and the user selects 11, 13 and 16. How would I filter the model from the selected options?</p>
  <p>Also, I think I need to change the selected options to a range so the above would become, 10-11, 12-13 and 15-16 so the range filter can work by using the <code>gt</code> and <code>lt</code> args. However, maybe a range filter won't work for this?</p>
  <h3>EDIT</h3>
  <p>In SQL I can do the below, which returns what I am expecting to see so I just need to convert this into elasticsearch syntax via Searchkick.</p>
  <pre><code>  select * from events
    where (min_age &lt;= 11 AND max_age &gt;= 11)
    OR (min_age &lt;= 13 AND max_age &gt;= 13)
    OR (min_age &lt;= 16 AND max_age &gt;= 16)
  </code></pre>