Allow inputs to be disabled

Including combobox, datepicker, numberpicker and select.

The actual input components aren't passed `disabled={this.props.disabled}` because they're all transferred the props anyway.
Merge branch 'disabled-inputs' of https://github.com/ojame/react-widgets into patch

Conflicts:
	src/pickers/datepicker.jsx
	src/select/select.jsx
release