normal key
normal key

Also we have to provide an ability use several options with same IDs, which is prohibited by react, but not strictly prohibited by select.
so, best solution seems to be
```js
      const key = 'option-' + k + '-' + id;
      return (<option key={key} value={id} {...itemParams}>{text}</option>);
```
And about sanitizing: was not sure, if react could use _any_ string as a key. Had to [check](https://facebook.github.io/react/docs/reconciliation.html#keys)
So now it seems to solve the problem
rkit/react-select2-wrapper