Label dosen't work in select field

If we try to pass the label option to a select, it doesn't render the label correctly.

Example:
```
f.select :year, options_for_select((1996..2014).to_a.reverse), :label => 'Some label'
```

But label displays as Year and not as 'Some lablel'.

Moved from: https://github.com/potenza/bootstrap_form/issues/36
Original creator: @extrim