renameColumn not working?

I wonder if I'm doing something wrong or if it is just not working:

```js
QueryGenerator.prototype.renameColumnQuery = function(tableName, attrNameBefore, attributes) {
    var attrNameAfter = Object.keys(attributes)[0]
      , columns       = [
                          { name: attrNameBefore, dataType: attributes[attrNameAfter] },
                          { name: attrNameAfter,  dataType: attributes[attrNameAfter] }
                        ]
      , model         = this.sql.define({ name: tableName, columns: columns })
      , scope         = model.alter().renameColumn(model.get(attrNameBefore), model.get(attrNameAfter))

    return this.evaluate(scope.toQuery())
  }
```

The `columns` are containing the following array:

```js
[ { name: 'signature',
    dataType: 'VARCHAR(255) NOT NULL DEFAULT \'Signature\'' },
  { name: 'sig',
    dataType: 'VARCHAR(255) NOT NULL DEFAULT \'Signature\'' } ]
```

According to the tests, I'd expected that it would just work. But for some reason, node-sql is complaining about a missing dataType :(