title: Knex does not return insert Id
body: <p>This is my table(CELLID) structure.</p>
  
  <pre><code>+---------+------------+------+-----+---------+-------+
  | Field   | Type       | Null | Key | Default | Extra |
  +---------+------------+------+-----+---------+-------+
  | CELL_ID | int(11)    | NO   | PRI | NULL    |       |
  | STATUS  | tinyint(4) | NO   |     | NULL    |       |
  +---------+------------+------+-----+---------+-------+
  </code></pre>
  
  <p>And this is my code to insert into the table.</p>
  
  <pre><code>knex('CELLID').insert(insertObj)
      .then(function (result) {
        _log.info(reqContainer.uuid, "Successfully Added To CELLID||", result)
        // respond back to request
        _log.info(reqContainer.uuid, "Exiting CELLID_S");
        return resolve(result)  // respond back to request
      })
      .catch(function (err) {
  
        _log.error(reqContainer.uuid, "Failed Adding To CELLID ||", err)
        _log.error(reqContainer.uuid, "Exiting CELLID_S");
        // respond back to request
        return reject(Error("Failed Adding CELLID"));
      })
  </code></pre>
  
  <p>After a successful insert, the Id has to be returned.This does not happen in my case. I always get and Id of 0 on an insert.</p>
  
  <p>I had tried by adding an extra column, auto-increment primary key ID(removing CELL_ID as PK).In this case, I get the ID(auto-increment value).</p>
  
  <p>What am I missing here?</p>
  
  <p>Thanks.</p>