update

changelog:

- support a placeholder
- use specific locale if moment is loaded
- the demo page loads moment from cdn
- the demo page presents different usages

known issues:

- can not format the output if moment is not loaded (but the component does not load moment anymore)
- [pikaday forces me](https://github.com/dbushell/Pikaday/issues/67) to change the [global 'locale' of moment](http://momentjs.com/docs/#/i18n/) to get the i18nized date output