fix respond_to? for non selected column

`post = Post.select("'title' as post_title").first`

In the above case when `post.body` is invoked then an exception is
raised since `body` attribute is not selected. Howevere `respond_to?`
did not behave correctly.

```
pos.respond_to?(:body) #=> true
```

Reason was that ActiveRecord calls `super` to pass the call to
`ActiveModel` and all the columns are defined on `ActiveModel`.

Fix is to actually check if the data returned from the db contains
the data for column in question.