"disable" binding doesn't work with "select" elements

[eriverosr]

Hello! I think I have found a bug with "disable" binding:

When used with a "select" element, it just adds "disabled" to select classes. I think it should behave as a input, button or text area. I was checking the source code and the problem appears to be between the lines 255-265:

 enable = (elem) ->
  if elem.is('button') or elem.is('input') or elem.is('textarea')
    elem.removeAttr('disabled')
  else
    elem.removeClass('disabled')

disable = (elem) ->
  if elem.is('button') or elem.is('input') or elem.is('textarea')
    elem.attr('disabled', 'disabled')
  else
    elem.addClass('disabled')

I think it should be this way:

enable = (elem) ->
  if elem.is('button') or elem.is('input') or elem.is('textarea') or elem.is('select')
    elem.removeAttr('disabled')
  else
    elem.removeClass('disabled')

disable = (elem) ->
  if elem.is('button') or elem.is('input') or elem.is('textarea') or elem.is('select')
    elem.attr('disabled', 'disabled')
  else
    elem.addClass('disabled')

Thanks for the library! It's very useful to me right now.