ignore text type columns from column_names_for_tally

I found a bug using `kaminari` if I have a `text` type column paginationhelper  does not work

so for something like this does, `paginate` helper does not work

    Model.plusminus_tally.page(0)    

`column_names_for_tally`  includes all the columns that should be included in the group by
I changed it to exclude columns with `text` type. 

it might or it might not be a good idea, I do not know why it fails or if it should be fixed in `kaminari`