Normalize form element `text-transform`

By default, browsers set `text-transform:none` on most form controls in
order to prevent `text-transform` being inherited from ancestor nodes.

However, the `button` and `select` elements are exceptions.

* Firefox and Opera do not apply `text-transform:none` to `select`.

* Chrome, Safari, and IE 8+ do not apply `text-transform:none` to
  `button.

It's not suitable to set `text-transform:inherit` because all other form
elements intentionally avoid it. Safari will not honour that style for
`select`, and Chrome will only do so when the `select` element is
clicked.

Further details:
http://tjvantoll.com/2012/07/10/default-browser-handling-of-the-css-text-transform-property/