Use the `input` event instead of `change`

This way, the handler is called even if you paste or drag text into
the box. It’s also more responsive (faster) compared to `change` or
`keyup`/`keydown`.

See http://mathiasbynens.be/notes/oninput for details.
Merge pull request #1 from mathiasbynens/oninput-ftw

Use the `input` event instead of `change`