Options validation for preset

Validate the entire tree of options passed to preset.

Maybe, each plugin can export a list of options that only babili preset understands and we can validate them only when using the preset and not when using the plugin separately.

```js
module.exports = function plugin() {};
module.exports.options = PropTypes.object({
n: PropTypes.number
});
```

Or, this can be implemented in babel - where validator is built into babel for plugins and presets.

```js
function plugin({ PropTypes }) {
return {
visitor: {...}
options: PropTypes.object({
n: PropTypes.number
})
};
}
```