title: Ignited Datatables for Codeigniter returns invalid SQL query when used with mysql's date_format function
body: <p>When i use <code>date_format</code>, it returns invalid sql query</p>
  
  <pre><code> $this-&gt;load-&gt;library('Datatables');
   $this-&gt;datatables-&gt;from('events');
   $this-&gt;datatables-select('id,event_name,event_location,DATE_FORMAT(event_start_date,"%b %d %Y, %h:%i %p") as evs,event_type_id,event_status');         echo
   $this-&gt;datatables-&gt;generate();
  </code></pre>
  
  <p>It returns </p>
  
  <pre><code>SELECT `id`, `event_name`, `event_location`, DATE_FORMAT(event_start_date, `"%b` %d %Y, `%h:%i` %p") as evs, `event_type_id`, `event_status` FROM (`events`) ORDER BY `event_name` asc LIMIT 10
  </code></pre>